Dave Winer: A perennial problem with RSS is how does the publisher force an unsubscribe? Shouldn't the publisher have the right to opt-out? Right now there is no mechanism that's broadly supported by aggregators.
Randy: I disagree. HTTP has an built-in mechanism for forcing an unsubscribe and if your blogging client doesn't support it, then it's incomplete. The mechanism is to respond w/ an HTTP 410 status code, that is, resource is Gone.
RFC: The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server's site.
Randy