It's usually small unique signature campaigns that do well. Since the signatures haven't been seen often or looks unique there should be a few people clicking away at it. With bit-x and bitmixer, it has become part of the forum. There are lots of people wearing it and we get so used to it we don't notice it.
Well i think its pretty effective because you see it alot wouldn't that make you curious that they can pay lots of members and also they've been running it for a long time.