There are more than one mechanism that can be employed to thwart spammers and some of the alternatives are in use here, with obvious good effect.
You'll notice from time to time that an admin has had to approve a post and 'bump' the post up so people can see it. That's part of it. Personally I try to get on at least twice a day to see if any posts need approval and to jump in and ramble on and on and on and on and on and on and on but that's not always possible, for example if we're off touring, in which case I just ramble on and on and on and on and ...