[bmn_]

Lots of misunderstanding going on in the comments. Let me set your confusion right.

w3id.org is basically the same as purl.org, see https://en.wikipedia.org/wiki/Persistent_uniform_resource_lo... for a background explanation. They are services that promise to be extremely stable and long lived and where you coin permanent URLs for certain Web technologies (e.g. Link relations RFC 5988 §4.2, XML namespaces, …) that require an identifier that never changes. So in theory you can put any well-formed URI there because most of the time, software will just compare for URI equivalence (RFC 3986 §6), but if a user wants to, he can also dereference the resource identifier and possibly arrive at a human readable document describing what's going on, for example visit http://www.w3.org/2001/XMLSchema in your Web browser. You cannot do this with content addressable IDs (named hashes/ni scheme, IPFS, DHT), URNs (guid/uuid scheme), etc. In order to achieve that practical goal, the dereferenced document needs to be published on a Web host, and the domain name associated with the Web host needs to be under your control.

Now, for coining purls, you put in an indirection. When you lose control of your domain name, simply redirect to a new one. In practice this eliminates link rot. There are other things on the Web that make use of redirection mentioned among these comments, like archives and link shortening, but that's out of scope for purls – you are not supposed to coin purls for general Web documents like news articles (millions a years), but specific documents whose URI serves as an identifier for a schema description or the like (dozens a year).

The difference between the different purl services is their governance model. IMO w3id is best aligned with the interests of hackers that make use of Web technology.