Are they? Please see
http://en.wikipedia.org/wiki/Special:Export/Main_Page (and
the XML dumps) - you can usually get the user ID from his user page this way, or
any other page he has edited; also note that the Stewards can use the user IDs
instead of the user names. I think it's better to have the user IDs public, to
have a unique identifier of each user, and not to have problems with non-latin
usernames. You can't do anything dangerous with the user ID (if you can, this is
a bug which should be fixed, but I know no such bug).
True. Still, what would you
need the user ID for?
Roan Kattouw (Catrope)