I'm sure that people exist who vote in multiple states - your friends are exhibit "A".
But - the real problem is discrepancies in the voter rolls - dead voters, voters that have moved but not been removed from the rolls, and so on. Dishonest precinct workers can cast those ballots all day long. How else do you think that so many precincts come up with 90, 100, 105 percent turnouts?
To continue - WV just purged nearly 50,000 from their voter rolls. In a state with just a little over a million registered voters, would 50,000 make a difference? You betcha.