In 24 hours the Pillsbury Facebook page went from 30,000 likes to 80,000 likes. All sparked by a coupon for money off their frosting range. Target is experiencing an amazing growth in fans by offering 25 x $25 vouchers, resulting in over 500,000 fans this week.
Samsung has gone a different route. They are promoting their Samsung Galaxy with art drawn on their phones. In order to enter, you have to tweet a request to them, and they will get an artist to create the best art suggestions. This has generated 400,000+ likes this week.
In all cases, the companies use the Facebook landing page to serve one page to their new visitors and one to their fans with the competition instructions. One the second page, Samsung have used Involver to encourage sharing to other networks. Pillsbury have told people to go the their website to register to win. Target have said that they will select winners from their group of fans. In Australia at least the Target competition would probably require a license to run their competition.
The key here is that all these brands are promoting engagement with their product. Pillsbury have told fans to go to their website to register, Target are giving away vouchers, Samsung have got people talking about the features of their phone.