If I recall correctly there was a thread about this issue on the forum already. At one point I was tempted to start advertising on Facebook but after reading about this I am glad I didn't! At some point I also felt the same for adwords, as I used a coupon given to me by a friend, and I noticed how quick the coupon ran dry without any conversions (took only 2 hours to consume the 50 euro's). The bounce rate was exceptionally high for the laser targeted keywords I was using for that campaign. Since that happened, I don't trust PPC anymore, I feel it's quite easy to mess around with it. This is just my exerience as I am sure there are loads of people that have had big success with PPC.

Yes I would stay clear of them. Did you also read about how Zuckerberg tumbled out of the top 10 of richest entrepreneurs, I think just after this became public knowledge? I am wondering if their is a direct correlation between this happening and him losing his top 10 listing..