Tommybs - 9:12 am on Jun 29, 2011 (gmt 0)
If you create an iframe app, you can then add this as a tab and have all your own logic in the code that handles the giveaway. One thing I would note is, that you're not allowed to run competitions on the facebook wall and I don't think on any of their apps, and in theory you're not even meant to announce your winners on the wall. You can capture email on an iframe app though. Now I know of at least one big company that does announce winners on the wall ( they don't actually run the comp on it) and they don't seem to have got in trouble, but then it could be because they are a big company. N.B you also can't use 'likes' as a competition entry. But you can of course limit the comp to only people who have liked your page. With an iframe app there is a way to test if a user likes your page or not, so then it's just a question of creating your page that has the comp logic. Hope this helps.
[facebook.com...] has some info, but you might need to search for the rest of it (I can't find a link at the moment)