As I see it, only a bunch of people keeps maintaining the Wiki. Since the HA Forums already have a quite solid anti-spammer registration procedure, why not leverage it then?
I'd rather we disable online registration. I'm kinda tired reading the "Recent Changes" page just to discover that 80%+ of the changes are either vandalism or blocking a spammer.
The worst spammer was notably one idiot who totally deleted one page and replace it with invisible links.
However, there's more serious issue: What if someone edit a page, not noticing that it has been vandalised? Now the Wiki maintainers face a difficult issue: If he/she tries to restore to the pre-vandalised version, the latest edits are gone. Or he/she can try to remove the spam him-/her-self. Yeah, fat chance.
EDIT: Oh no, the "Recommended Ogg Vorgis" page has gone into Wikiness Protection Program... I can now no longer edit it... oh! The Humanity!...