I like that it gives you an insight into your potential customers' interests, their shopping habits etc which has been really useful in helping me target my marketing campaigns more effectively! The only thing i dislike about friend buy was when they changed how many times someone could be added as interested/browsing before being removed from list but this can't always happen so not too much of a problem now - we have made great progress since implementing FB advertising!! If anything just do what everyone else does (it's simple!) if nothing happens then there isn;t any harm done other than giving yourself some time for things perhaps get used by others who will enjoy using them :).
We are able reach out specifically towards our customer base with targeted ads where previously these were never reached due lack or targeting criteria.