I've used it with minimal success. Conversion is tough; people are in "social" mode, rather than "purchase" mode. I've seen some techniques, where you utilize the pay-per-impression ("x" amount of $ per every 1,000 impressions). If you are clever, and can get a high enough click-through rate, people have managed to pay less than $ 0.01 per click. Done with proper targeting, it could be a profitable venture.
The price of advertising on the world's biggest social network appears to be on the rise. The average cost of purchasing pay-per-click ads on Facebook rose by 22% in a single quarter, according to a new report by digital marketing platform provider Efficient Frontier.