Actually, it's a good idea. In no way is it a
invasion of
privacy. Anyone who wants to get some idea of a contributor's
interests can look at his edit record. There's no good reason
not to have watchlists be public.
Edit history does not equal watch list. I can watch something without
having edited it. And other people being able to see my watch list is
an invasion of privacy of sorts, so this should be "opt-in" only, not
the default, if implemented.
Wikipedia is trying to get more people to join, so it would be a tragedy
if this privacy issue kept folks away.
-Fuzheado