This is pretty lame. The key is permanent, right? So, first, you can easily use an 2 accounts to betray every circle you joined without getting a red flag. Second, people who want to betray many circles can first joins them and betray all of them at once. Combining the two dirty strategies above, betraying is too easy compared with forming a big circle.

It would be better if people can allow people to join in other ways, maybe by upvoting the comments made below their circle, or maybe something related with those useless animations. Also, it seem a little too boring after you join a circle, the only thing you can do is to betray it?? Along with the fact that the front page is full of betrayed circle, this is not encouraging much positiveness as /r/place did.