Facebook is about social networking. This is how things are done now. It's the modern-day equivalent of seeing somebody in the bookstore and saying, "Say, aren't you Judy? I'm a friend of Bob. I saw you in that group picture he's got hanging in his apartment."There was a time when "I've seen you around for a while and I wanted to meet you" was not considered stalking, but rather normal Human mating behavior. There's no reason why a friend request from a mutual friend on Facebook should be considered creepy.
Yes, but "I've seen you around" is something that happens out in the real world. That's not the same thing as trying to meet a girl you don't know through Facebook. And no, it's not the same as actually physically stalking someone, but that doesn't change the fact that it doesn't come off well at all as a way of meeting someone.
No, it's the modern day equivalent of staking out the bookstore until Judy arrives, and then following her around at a distance and picking up the books she looks at to figure out what she's interested in.