Encouraging voter participation of marginal legality is nothing new for the Obama campaign. In 2008, they had an elaborate web portal for college students, encouraging some to register to vote where they went to school, discouraging others. The overall goal was to get students attending college in battleground states registered to vote in those states regardless of their actual domicile. If students from a battleground state went to college in a safe red or blue state, they were encouraged to keep their registration in their home battleground state.
The Obama campaign website in 2008 never told the students to cancel their original voter registration. Nor did it provide guidelines for what constituted bona fide domicile.
Currently, voter watchdog groups like True the Vote are conducting data crunching to determine who may have violated federal election law in 2008 by voting in two states for president. If someone does it again in 2012, it will eventually be caught thanks to the efforts of private parties combing voter rolls.