Half the reason people don't have success with FB is because they're trying to get people to buy the same shit that shows up fucking everywhere. Diet pills, Dating, and Evony.
Ok, that shit does work, but only in a very very broad sense.
In my experience Facebook is about targeting, getting it right, and scaling... And free trial shit with a $30 pay per lead doesn't cut it.
I do nicely in a very specific niche where the average payout is 1.8%-3.5%... but we're talking on items that start at $2,000 per sale. Facebook is actually the perfect place for this, believe it or not. Now, I don't pull in shit loads of cash that'll allow me to retire off of it, but only because I'm too fucking lazy to expand on my campaigns.
Stop thinking of the same shit as everyone else, and actually think about what being able to target people by interest and demographic potentially means in what you can advertise to them.