Navagon: Yes, GOG should have measures in place to make it very difficult for spam bots to post and moderators to mop up what's left. But they've never had much in the way of moderation. They've got more than they used to, but the site's a hell of a lot more popular now and clearly more needs to be done.
They're a lot more alert about what happens on the forums though, spam removing among the wishlist comments seem much more sporadic. Users buybuybuy, online, and topbulk have posted spam as "comments" for several wishes. ##@@##@@, ericzhu, and adsadskjkk seem like the same kind, but are a lot less common.
... that's my impression from the currently 20 highest voted "this week".