My recent findings from Facebook UK advertising:-
Click discrepency of about 25% i.e. Fb: 100 clicks P202: 75 clicks
Loads of mobile devices. There's no way I can find to filter them so you are being forced to pay for them. Better send to a mobile offer, look at $_SERVER['HTTP_USER_AGENT'] in php and redirect from there. If you are promoting something completely unrelated to any mobile offers it's not going to convert anyway so just leave it as is. Someone suggested that there is a new app that displays adds that has become really popular. I haven't checked this out yet.
FB Geotargeting is all over the place at City and Country level.
CPC campaigns are doing all sorts of random stuff with bidding. Could be down to end of year budgets, increased spending over Xmas season having some affect on the algorithm.
CPM bidding is more reliable but also more expensive in the long run.
Split testing landing pages can get campaigns pulled even if its something small and silly like a different background colour.
Add approval is carried out by the monkey from the Cadburys advert who hits one drum for yes and the other for no.
The monkey is shown a screenshot of the landing page which is taken by a linux bot running firefox immediately after the campaign is submitted.
Alot of the things I've been seeing have reminded me of what we've all been through with Google. I think facebook is eventually going to go down the same path and it wont be long before all kinds of factors influence if your add gets shown or not:- Landing page quality score, account history, bounce rate etc.
Looks like it's going to be fun and games in 2011.