CNN reports that the number of people who commit voter fraud is likely to be no higher than those to be hit by lightning.
How big is that number? According to USA Today:
During every minute of every day, roughly 1,800 thunderstorms are creating lightning somewhere on Earth. Though the chances of being struck by lightning are estimated at 1 in 700,000, these huge electrical sparks are one of the leading causes of weather-related deaths in the USA each year with an average of 73 people killed; about 300 people usually are injured by lightning.
Also, again according to USA Today: In California, for example, there were 469 cases of fraudulent voter registration resolved from 1994 to 2003, compared with 253 cases of voting fraud, according to a study in the book from Michael Alvarez of the California Institute of Technology.
If the presidential election is decided by no more than 300 votes, let's demand a hand count. Otherwise, I'd watch out for lightning, if I were you.