You need to read this article.
Jon Stokes has written a very detailed, very compelling overview of exactly how simple and straightforward it is to alter how electronic voting machines tabulate votes.
Before you say that's just a paranoid delusion, ask yourself whether it sounds plausible that one person could cause hundreds of millions of dollars damage to American businesses and households. Then think about the anonymous hacker whose cooking up the next worm or virus that will turn your computer into a big ugly paperweight.
It's truly worth a read.