The last 6 months I've heard the sentence 'hey lets build a facebook app' from clueless agency people more times than I care to remember.
When you ask why - there's generally not an answer.
Well, okay ... there IS an answer. It provides revenue to the agency that build it.
Are they a scam? In 99% of cases I think they are. Just like some iPhone apps (I wouldn't want to be the person who thought the Toyota dealer locator app for iPhone was a smasher of a concept ...)
Check this out - http://www.new.facebook.com/apps/application.php?id=5588308018
I was served up an add to take their cheese toast challenge today on facebook - problem is I live in Victoria, a place where (thankfully) Sizzler doesn't have any locations.
How does this provide anything useful to the user? And what are they doing wasting their media dollars targeting people who can't visit their restaurants?