Bruce Schneier has an interesting write-up on the security procedures of the papal elections.
they're quite elaborate and, as he points out, quite secure. over the last thousand years, they've done a pretty good job of preventing just about any kind of voter fraud that could be imagined.
what really gets me about the whole thing is that with all of this obvious thought having been put into ensuring fairness and transparency, it's clear that the cardinals don't trust each other very far (or at least historically haven't). all of those cardinals are supposed to be holy, moral, ethical men, but if there had never been problems, no one would have bothered coming up with and codifying all these elaborate safeguards. so clearly at least a few bad apples have made it through. yet, once one of them is elected pope, he is elevated to the holiest office in the world and is considered to speak directly for god.
it reminds me of Bill Hicks' observation on the popemobile and its inch thick bulletproof plexiglass: "that's faith in action, folks."