This is a small one (and it might have been brought up before, in which case I apologize):

I'm perennially surprised how many users apparently don't test their URL in their user profiles after entering it. Many seem to omit the "http://" prefix, which causes the system to link internally (like http://www.typophile.com/user/www.domain.com/), which is annoying and doesn't make any sense.

While this is obviously user error, the system could help prevent it.
Since I can't conceive of a single instance where this internal linking could be useful: Could this script be changed to (1) detect whether the "http://" (or similar protocol) prefix has been entered, and (2) if it hasn't, auto-add "http://" to make a functioning external link?