Wouldn't this promote political racketeering? If the Mob bought one local canidate for a local office and sees that you gave money to another party, then they could know whose legs to break.
Also why should someone be exposed if they supported someone who their neighbors didn't support. People should have the right to support whomever they wish without fear of peer pressure.
Personally I don't like these kinds of hacks. They are very divisive (e.g. United States Of Canada/JesusLand silliness) and tend to create arguments between the majority and minority voters of a population. The only benefit I see is to boast the egotism of people who vote together (not a good thing). I've never seen this kind of data promote any useful discussion at all.