I wouldn't have used the same language as the parent, but every time a developer creates a FB-only login, it promotes the idea that it is acceptable. It is not.

Sure it is acceptable.

I accept it.

It really isn't acceptable to force someone else to sign up for one service to use a new service.

How many potential clients are they really excluding here? In other words how many people would use this service and not already have a facebook account?

I have one, but I categorically refuse to use Facebook to log in anywhere. In other words, if you look at how many have a Facebook account, you're looking at the wrong number.

OK perhaps that was a tad harsh, but I do get annoyed when I see the only login option for something be Facebook. I won't go on an anti-Facebook tirade but suffice to say it is not everyone's cup of tea and not everyone has a Facebook account. I suppose given this is just a technical demo it is acceptable.