So here is where FB's Achilles Heel may lie. On one hand, it's great that it stores pictures and stuff. But on the other .. do you really want your pictures and personal information out there? (Besides, even if your profile is private, pictures can still be linked/shared, if you get the raw .jpg url.) Maybe we (as tech nerds) are just more aware of these caveats whereas most people trust FB like they would trust a family photo album under the couch.
(Missed schmozz's comment below, I link we are trying to say somethig similar. Google Plus's major failing is discoverability.)
Google tried to address this with circles, which Facebook responded to and implemented a similar solution, but I think most people just don't like to classify their 'Friends' when first accepting a connection and are very unlikely to reclassify them later.
People post personal info (pictures, status updates, etc.) on Facebook, and I think the expectation when you accept a friend request is that the requester will at least make a cursory glance through your profile. If you, out of the blue, request someone you've never spoken too, I'd say a reduction in the creepiness factor could be sending along a message with the request saying "Hey, I've seen you around in class, I'm dvt".
If there doesn't seem to a be any rhyme or reason to the out of the blue friend request, someone could just make the assumption you just want to look through their profile at their pictures and stuff.