How are you doing analytics tracking ? - if you're using GA or something similar then it could well be that the GA code isn't loading before the user bounces. If you check your webserver logs that should give you an indication if that's the case.
By the way, I'm not the only one reporting this issue: http://www.google.com/#sclient=psy&hl=en&q=facebook+...
If you're working in a more "black hat" corner of the ecommerce world like affiliate links, it's certainly possible that click fraud occurs, I just haven't seen it occurring.
Have you checked the analytics reports that Facebook generate to see if it is the same users clicking the advert over-and-over again ?