I agree with the subject line of this e-mail wholeheartedly.
May I suggest that the best way to prevent vote-stacking would be to stop voting?
(Someone responds here that we need voting for AfD)
I point out that we don't need voting for AfD, which is why we changed it away from VfD, and that the proper way to close an AfD is to look at the arguments and how they adhere to Wikipedia policy, and remembering that if a bunch of people come from off-site to express their belief that an article should be kept, THAT SHOULD BE TAKEN SERIOUSLY, because Wikipedia is for its readers. That doesn't mean their votes count more, less, or the same as everyone else's, because AfD isn't supposed to be a vote.
Really, AfD votestacking isn't even the most destructive - we've always been pretty good at ignoring meatpuppets if we want to, at times even when we shouldn't. The dangerous votestacking is the "Get all your friends to pile on to an RfC, RfA, or policy debate."
Which is why we should stop voting on those as well.
-Phil