Why is Facebook not allowing the use of FB Connect or Social Plug-Ins (such as Like, Recommend) for online gambling sites, even in countries where it's legal?

While there is little stigma around betting/gambling in social circles in the UK, other societies take a far more dim view of gambling. PayPal/eBay, Visa/MasterCard and other large companies (Americans are puritans, did  you say? :)) with a global footprint would rather not associate themselves with gambling at all, if it wasn't for the compelling economics. Facebook just doesn't want to associate itself with gambling firms, for now. It's like asking why http://Google.com or Microsoft don't  do the single-sign-on from their ecosystems to betting sites: corporate strategy, driven by American shareholders. It's certainly not a legal concern - the top gambling firms are all licensed, regulated, and overseen by governments...including those from France, Italy, UK, Denmark and Spain.

Facebook is based in the USA and is a global website (in so far it doesn't operate separate http://.co.uk, .fr or .it domains) but it has a very heavy US bias. There is no reason for a company such as that to try and profit from the online gambling industry due to the legal implications in the US and so a decision was no doubt made world wide but with a leaning from the location of their domestic operations. And to answer Mr. Collicoat in the case of Paypal, the decision by them was nothing to do with any legal aspects at the time. More accurately it was pressure from the US Government after they were purchased by eBay, they being a company located in the USA, to prevent the availability of gambling to US citizens.

Just my opinion. The real reason is that facebook does not like gambling sites, nor did paypal or a host of other operators, they will tell you its about security, international laws and the like, but they really dont want people posting winning staus posts from gambiling sites, it may detract from the facebook revenue economy.