How many scammers/spammers?
Isn't group B a lot larger than group A? Isn't even group A a little scammy? Does Kellogg's want access to my info to help me, or because they want to show me more cereal ads?
You're starting off putting yourself in group B, which is not a good idea at all. Facebook is acquiring a very negative user reputation, along the lines of Ebay and Paypal. That doesn't mean that people will stop using it, but there's very little trust for Facebook - Facebook has done everything in its power to demonstrate that it is not trustworthy.
Facebook can't be trusted to keep your data private, and you're lumping yourself in with them. Seems like a bad plan to me.
Clicking "let this company I've never heard of suck down all my Facebook information" is a terrible idea. It's like downloading and running an executable from ugothacked.ru. Except you can't even wipe your computer and reinstall - it's irrevocable.
We planned on using an Independent login along with FB and Twitter, but was planning to skimp on putting a lot of thought in to the Independent login. Would that not be prudent anymore? I would like to hear your thoughts (and of others).