Perhaps a better way of wording it would be that facebook-only friends are not actual friends.
It is like that old joke: How can you tell how many friends a facebook user has?
Don't worry, they will tell you.
Facebook is a great way to maintain contact with your real friends and family. I get a bit leery when people claim to make "friends" with people they have never actually met or talked to.
It all boils down to what each person's definition of "friend" is.
To me, a friend is something really special. I only have about 2-3 friends and I consider myself very lucky. I have a buttload of acquaintances. But they are not the same as friends.
But, other people have a more liberal definition of friend. And that's ok.