Reminds me of what I see on my Wordpress Blog: lot's of 0-content comments like "this is a cool article". At first they didn't make sense (blocked them anyway), but then I remembered the Wordpress settings for comments. By default, it is set to "commentors must have been approved at least once". So I guess if I would let one of those innocent comments through, they would be back with more serious stuff.
Spammers are crafty...