Vote fraud has been going on to some extent forever, especially rife in 19th Century politics. It is actually easier to vote, but harder to cheat than ever before.
http://en.wikipedia.org/wiki/List_of_controversial_elections
It may be more difficult to cheat, although it sure does not seem that way, but unless those with authority to make corrections do so then in the end it pays.
Vote fraud probably is able to generate only a few percentages of the total vote, but in close elections it is just enough. Once its seen to succeed, its likely to increase not decrease in occurance.