Sometimes, where there's smoke there is just smoke.

President Obama won 100% of the vote in 59 precincts in Philadelphia.  This sounds an awful lot like the kind of percentage one expects in a dictatorship.  After all, isn't it statistically impossible to win by such a margin?  In a country (with a diverse population), yes.  But not in a precinct with homogeneous demographics.

(Full article).
Certain watchers cried, "foul!" regarding what appeared to be %150 voter turnout in certain parts of south Florida.  As it turns out, sometimes, where there is smoke there is just smoke.  The county simply counted each page of the ballot rather than each ballot: turnout was half of what was reported (two pages per ballot).  There may have been some serious glitches in this election, but Philly and south Florida provide no evidence of systematic fraud (yet, in any case).