My unofficial theory is that Facebook prefers ads that make people sign up for Facebook pages — although maybe those conversion rates are higher because Facebook users like to do things on Facebook. But one thing I learned with Facebook ads is that you really have to play with the copy and the image to see what hits. With your ads you have to think of yourself as designing viral content rather than just ads:

http://news.cnet.com/8301-1023_3-57513266-93/ad-fab-hot-star...