The internet's first commercial era was, in retrospect, strikingly passive. Early websites were largely static pages published by one party and consumed by everyone else: a library you could browse but not write in. Tim O'Reilly's widely cited 2005 essay on "Web 2.0" named what came next — a read-write web built on user-generated content, social platforms and services that got more useful the more people contributed to them (O'Reilly, 2005). The catch, which became clearer as Web 2.0 matured into the platform economy of the 2010s, is that "read-write" did not mean "co-owned." A creator's videos, a reviewer's ratings and a seller's customer relationships all lived on infrastructure a platform owned outright; the platform could change the rules, the algorithm or the revenue split at will, because the people generating the value held no stake in the network itself.

Chris Dixon's Read Write Own: Building the Next Era of the Internet (Dixon, 2024) names a proposed third era: read-write-own, in which blockchain-based networks let the people who use and build on a network hold an actual, portable stake in it — a token representing partial ownership or governance rights, rather than a username on someone else's server. It is worth being clear-eyed about the source: Dixon is a general partner at the venture capital firm Andreessen Horowitz with a direct financial interest in blockchain adoption succeeding, which does not make the "read-write-own" framing wrong, but does mean it should be read as an argument from an interested party rather than a neutral history. Whether decentralised ownership actually changes outcomes for most users, or simply shifts who extracts the value, is one of this module's live questions rather than a settled conclusion.

Stripped of the hype on both sides, a blockchain is a distributed, append-only ledger: a record of transactions or state changes, replicated across many independent computers ("nodes") rather than held by one central authority, with each new block of entries cryptographically linked to the one before it so that altering a past entry would require redoing every block after it, across enough of the network to control it (Nakamoto, 2008, describing Bitcoin's original design). Nodes agree on which transactions are valid through a consensus mechanism — Bitcoin's proof-of-work has every node compete to solve a costly computational puzzle, while newer designs such as proof-of-stake (which Ethereum adopted in September 2022) have nodes post collateral instead, validating transactions without the energy-intensive competition. The mechanism matters more than the word "blockchain" itself: two systems built on the same underlying idea can have very different costs and risk profiles.

What problem this actually solves is narrower than it sounds: it lets parties who do not inherently trust each other, or a shared intermediary, agree on a single record without one party controlling it (Catalini and Gans, 2020). That is valuable in specific situations — multi-party supply chains, cross-border payments, any record several organisations need to trust equally — and largely redundant where a trusted intermediary already exists and works. It is not free. Throughput is limited compared with a conventional database; proof-of-work's energy use is real and measurable — the Cambridge Centre for Alternative Finance's Bitcoin Electricity Consumption Index put Bitcoin mining's 2023 annual electricity use at roughly 120 TWh, within a wide estimated range, comparable to a mid-sized country (Cambridge Centre for Alternative Finance, 2024) — though that figure describes one consensus mechanism, not blockchain as a category, since proof-of-stake networks use a small fraction of the energy. Complexity is a cost too: smart contracts can contain bugs, and lost cryptographic keys cannot be recovered by calling a help desk.

A token is simply a unit recorded on a blockchain representing some right within a network — access to a service, a vote in how the network is governed, or a verifiable claim about an asset's provenance or history (Catalini and Gans, 2020). None of that requires a token to behave like a currency or an investment. An access token that unlocks a feature, a governance token that lets a community of users vote on a protocol's rules, and a provenance token that certifies an item's unaltered history are all functional: their value comes from the right they confer, not from betting that someone else will pay more for them later. The "ownership economy" label that Dixon (2024) and others apply to this layer is really describing these functional uses — a stake in a network's governance or economics, not a speculative instrument.

In practice, functional and speculative uses get conflated constantly, and the conflation causes bad decisions on both sides: a genuinely useful access or provenance token gets dismissed as "just crypto" because the market around it is dominated by speculation, while a purely speculative token gets adopted on the strength of a functional-sounding pitch it doesn't deliver on. The speculative side is real and has caused real harm — the collapse of the FTX exchange in November 2022 and the broader "crypto winter" that followed are well-documented cautionary examples of excess built on little functional use. Regulators have responded accordingly: the EU's Markets in Crypto-Assets Regulation (MiCA) became fully applicable across the EU on 30 December 2024, bringing crypto-asset issuers and service providers under a formal licensing regime (European Union, 2023); the UK has chosen a separate path, legislating in February 2026 to bring cryptoassets, including stablecoin issuance, within the Financial Conduct Authority's remit, with the FCA's final rules published in June 2026, an authorisation gateway open from 30 September 2026 to 28 February 2027, and the regime itself due to take effect on 25 October 2027 (Financial Conduct Authority, 2026). Both regimes are moving targets — verify the current position before relying on either for a live decision. Nothing in this module should be read as advice on whether to hold, buy or sell any token or cryptocurrency; the question this module equips you to answer is what a given token actually does, not what it is worth.

A sound evaluation of any blockchain or web3 proposal asks four questions in a fixed order, because the order prevents the most common mistake — getting excited about the technology before checking whether the business problem is real. First, customer value: does this solve a specific, named problem for a specific customer, or is the blockchain element a novelty with no clear benefit over an existing, simpler solution? Second, feasibility: can it actually integrate with the organisation's existing systems and data, given that a blockchain's output is only as trustworthy as the data fed into it — a ledger that faithfully records bad data simply makes bad data harder to correct. Third, regulatory and reputational risk: does the proposal's specific design — a functional record versus a tradeable financial instrument — sit inside a regime like MiCA or the UK's emerging cryptoasset rules, and is that position stable enough to commit to. Fourth, cost: what does it cost to build and run relative to the benefit, including costs that have nothing to do with the blockchain itself, such as integrating with legacy systems.

The most common evaluation failure is treating "is blockchain the right technology" as the only question worth asking, when feasibility and cost are frequently the actual constraint. An organisation whose core transactional systems cannot yet produce clean, consistent, timely data has a data-quality problem that a blockchain will faithfully preserve, not fix — exactly the kind of legacy constraint explored when sequencing a technology roadmap in Module 2. Separating "this is a bad idea" from "this is a good idea blocked by something else" is the single most useful judgement this module can give a marketing manager facing a confident vendor pitch.