How do I know you?

A few months ago, I caved to Peer Pressure and joined Facebook.  While I am in my 20s, I find myself very out of place in the world of Social Media.  I think it's partly because I feel out of place socially in general.  I’m a little awkward.  So far, I have found some quirks in the Facebook system. 
It seems accounts can be 'hacked'.  This means that somebody posts ridiculous promotional items on my wall using bad spelling and grammar.  This isn’t a huge deal, because I can just delete the posts, but I do wonder how people have the skills to hack but not to spell.

Another thing that seems a bit weird to me is the whole ‘friending’ process.  I don’t quickly consider people my friends.  For example, a girl whose name I’d never heard before sent me a friend request.  I’m a little awkward handling this type of thing, so I asked how I knew her.  Her exact response: “Use to date R.C. We ate ice cream at Storheims one time and I remember u use to work in the shoe department at shopko I believe” 

I’m pretty sure we aren’t friends.  Another email chain went something like this:

Me: Sorry, and how do I know you?  Thanks! (see - I tried being polite)
Him: do you know me name sounds so familiar
Me: no

But then, I don’t request just anybody to be my friend.  Same in life, really.  A girl I worked with at my bookstore job joined Facebook, and I sent her a request.  She hit ‘Ignore’.  That’s what I get for taking the initiative friend-wise.  It does reinforce my awkwardness, though. 

Finally, there was a somewhat random friend request that I accepted.  A sort of regular customer from the bookstore asked if I was on Facebook.  He didn’t seem creepy, so I said ‘Yes’.  I let him know my name to search for me.  I accepted his request, and was a little bothered to see that he seemed obsessed with nun chucks performances, but didn’t think anything of it.  A few weeks later, I tried to look up his page, and sure enough, it doesn’t exist.  He’s apparently de-friended me, and blocked me from seeing his site.  Or maybe he’s just removed his Facebook page, and hasn’t come in to the bookstore since.  I’m a little offended that somebody I didn’t really want to ‘friend’ de-friended me.  Either that, or I just don’t get the whole Facebook thing anyway.

I think it's best if I stay away from Myspace and Twitter.