The Clevealnd Plain Dealer reports that there are 27,000 voters listed as active voters in both in Ohio and Florida. They could cast bellots in either, or both, states, according to their investigations: "virtually nothing prevents transient voters from casting ballots in multiple states."
Other papers have reported similar problems in Florida. The two counties with the most double regsitered voters are Cuyahoga County (OH) and Brovard County (FL). Apparently the Plain Dealer matched computer records for Ohio's 7.9 million active voters against Florida's 10.3 million. Good detail in the article, worth reading. Maybe the same people in Ohio and Florida will decide this election; wouldn't that be amusing.