"friends" on social networks

I wanted to get some opinions on what friends are on social networks. Owning a facebook, I have 154 friends. But are these people really true friends???
Looking through the list i notice I have many people I only met once that I never talked to. I also have alot of people I used to be good friends with but that moved or such, I talk to some of these people but not all.
Now I look at the definition of friend and here is what I find:

1. A person whom one knows, likes, and trusts.
2. A person whom one knows; an acquaintance.
3. A person with whom one is allied in a struggle or cause; a comrade.
4. One who supports, sympathizes with, or patronizes a group, cause, or movement: friends of the clean air movement.

To my great surprise I see that friend can also mean, an acquaintance (definition 2).
By that definition all my "friends" on facebook are friends.

I can now look at the first definition which for me is the most interesting and the most true, a person one likes and trusts. After looking through my list a good 70% go away, leaving about 45 friends.
My question is what do you consider a friend? Do you think this term has become overused and lost its initial meaning? Do you believe this is a good thing or is it more negative?
thank you very much