They can go fishing for who may have voted one way by setting up a fake website and getting people to give away information when the site is really pro-voters looking for people against it so that they can terrorize them either right before or after the vote is cast. Happened with a couple of fake Pro Proposition 8 websites that were actually people against Prop 8 in California years ago, collecting names of people to punish for not supporting same-sex marriage. I expect the same trick to be used again
Good point, Morpheus2009.