To be honest , .tk is a great idea. but they ruined it with steeling traffic and remove your domain with any reason.
But if the domain that you are using, is having very huge reputation, and have a link back to them, sometimes they will just let you off.
Perhaps they afraid that those famous site owners will write some very bad review about them, and caused people not dare to use their domain.
But then again, they forget that those small sites owners also do have influence in the online media as well.