I'm not worried about selling followers, because one of the bases of UA is that the more follows you have the less power it gives each of them. So someone with a high UA and not very many follows could sell a few follows and make a little, but returns would diminish quickly.

Case in point: almost immediately after I first looked at my score, Ausbitbank followed me - and my score went down a little. He's #7 in UA, so he has a lot to give out, but he also follows almost 3200 people, so it's very heavily diluted.