The recent winner of the "Win Dinner with Barack Obama" contest, which the Obama campaign has been running for the past year or so, was an actual Obama staffer. From Politico:
One of President Obama's own campaign staffers was chosen for the popular win-a-dinner contest with the president.
Toby Fallsgraff, apparently a member of the campaign's technical team, a wrote in a fundraising pitch that his name was drawn for the contest while he was testing the campaign's computer systems.
"Your chances of winning Dinner with Barack (and Michelle) are MUCH better than you might think," Fallsgraff wrote to supporters. "I know, because my name was randomly selected. That's because I donate at least once every time we do these contests just to check that the website is working properly for you and everyone else."
Which suggests the following: the only people who are entering these contests already work for Barack Obama. In November, he's clearly going to sweep that particular segment of the population.
The other segments are up for grabs.