There has to be a decent level of give and take. Give and take does not always come and go in equal doses, but if you are the one who always calls them up, or always has to initiate conversations and make plans to do stuff, or if you always do stuff for them (like helping them to move, or helping them set up their computer, or giving them rides or whatever it is) and they never or rarely do anything helpful or nice for you, then you have to ask yourself, why you would want those people as friends.
Do you notice that these people go off and do fun things like seeing movies, going to the mall, taking a road trip, going to a party (or throwing a party and not inviting you) with other people, but not you? Not good friend material.
Do you notice that these people ignore you, constantly interrupt you or blow you off when you are trying to engage them in a conversation? If so, they may either not be good friend material, or you may have some type of annoying conversational style, or you may appear to be desperate. That doesn’t make for being liked.
There is a very big difference between having friends and simply having acquaintences. There’s also a huge difference between really knowing people for real, in real life, seeing them often, talking to them in person, interacting with them in person, than there is with people you simply chat with online. It’s unfortunate that Facebook uses the term Friend because some of those people might be real friends, but most of them aren’t. They’re just causal or even super-ficial cyber-buddies. I don’t think it’s likely that people have thousands of friends, or even hundreds of friends, although you might actually know that many people.
The other thing that I’m concerned about, is that you are unsure of whether these people are your friends. Unless you have some type of situation, like having Aspberger’s Syndrome or something else that would make you unable to easily have regular social interactions (or to be able to interpret regular social interactions) it seems like you would know pretty readily whether people like you or not.
Why do you feel unsure?