Hrm. I think that'll lead to too many problems. First, what are they drawing for.
Second, and more importantly, we have to then decide who can use karma. If it's everybody, then this is straight out - people will get their friends to up their karma to keep them in the drawing (especially if better karma ratio implies better odds); on the flip side, people will spam the "smite" button for people they don't like to try to knock them out of the drawing.
On the other hand, if only admins can do that, then we *will* get accused of favoritism - "why did you applaud his shitty comment and not applaud mine?! I should have been in that drawing!" and other whiny crap comments that I don't want to deal with.