Files are probably the most widely-recognized metaphor for persisting digital information: an opaque container with whatever inside, to which an arbitrary label is attached. The URI, taking cues from the naming schemes of hierarchical file systems, extends this metaphor — with all its benefits and shortcomings — to the Web.
The first problem in this space is that people are really bad at naming things, a condition to which anyone with an Untitled-1 on their system can attest. Moreover, a computer's latent threat of discarding your hard work unless you choose a name right now does little to inspire creativity in this arena.
This problem is exacerbated by a second: you have no control over who or what links to you. Once you mint a URI, advertise its existence and reply to a request for it, that's it: it's out there
for good. Of course, the courteous thing to do is to keep your URIs the same — forever. This promise isn't so easy to keep when you can rename or delete resources on a whim.
However, our problem goes beyond mere courtesy and into the realm of serious business. In the mid-1990s, some guys made a bet that every link to a resource is a vote for its fitness. By proxy, this bet gave birth to an entire industry known as SEO. The net effect is this: if your resource got hastily named, giving it a better one without compensating for the original will likely do more harm than good. A final complication is that more pithy names — aside from being more helpful to people — are also found to contribute to this fitness rating, driving incentive to do so. Therefore: