It should not worry you. There is nothing in the TOS that says that anything over 18 % CTR is against the TOS. If you post such a statement you have to back it up man.
Hight Ctr should not be worrying if its genuine. Of course, if the CTR is ridicelouslyshould be worrying because I fail to see how someone can generate close to 100 clicks on say, even 100 impressions.