These services may not "shut down" but they might change (or have already changed) so much that many would not have signed up knowing what they know now. This i

These services may not "shut down" but they might change (or have already changed) so much that many would not have signed up knowing what they know now. This is kind of a danger of an open protocol too (for example, IRC users who signed up in 1998 to talk about Britney Spears gossip are probably not well-served by most current IRC networks), but not to the same extent.