Also why should I connect some (possibly clingy and untrustworthy) site with my facebook account even if there is a fat chance that I use it for the fist and the last time?
Why would you sign into a site were that was possible? Maybe I'm strange but I don't create credentials (no facebook so that's not going to be used) on a site or for a service unless I've become sure that I'm going to use it.
If I have to sign in before I can see anything about it, I leave.
You seem like a soothsayer to me as you know beforehand if you will use some site regularly or not possibly even before accessing its functionality (which is applicable to many sites with login requirements).
