I think I have too many books

Earlier this week, I found myself quite suddenly unemployed. In between my classes and the job search, I seem to be finding things to fix that didn't really need to be fixed at all. This afternoon, I started to attack the wall of books. I reorganized shelves 2 through 4 (pictured above) and now I have separated my Young Adult from Fiction/Literature, and I have Anthologies hanging in a pile waiting to find some space to squeeze into.

Of course, now that I've begun this, there's no turning back. Because now I have stacks of books all over my floor, and some decisions need to be made.

Many questions have been raised as I fiddle with these books.

Why do I hold on to mediocre books that I read years ago?
Do I really need all of those "Sisterhood of the Traveling Pants" books?
Should short story collections by a single author be shelved in fiction, or anthologies?
Am I ever going to decide I like Alice Hoffman again? Why do I still have like ten of her titles?
Why am I hanging on to ARCs?
Should I separate fairy tale collections from fairy tale criticism?
Should anthologies be alphabetized by title or editor?
Is it okay to get rid of books I was given as gifts if I didn't like them? (The books, not the gifter.)

WHEN AM I GOING TO HAVE TIME TO READ ALL OF THESE BOOKS??

...

Right. I need to purge some stuff. Because what you see there on that shelf is not everything I own. There's another shelf above what's shown, and a whole other wall of shelves to the left of those books. I also have piles neatly stacked against walls, and boxes of books hidden under the bed, and several more boxes up in the attic. According to my LibraryThing account, I have 970 books. I used to think that was a lot, but I recently met someone in one of my classes who told me she owned over 5,000 books. I was jealously horrified.

Mathematically, it's impossible to read all of these. Especially factoring in school reading (and I plan to be in school for the next decade or so), plus audiobooks loaded onto my iPod, and the library books I can't seem to stop borrowing. And then there's the inevitable used book sales that I can't seem to keep my tote bags away from.

It would definitely feel great to set a chunk of these books free, but I have no idea how to make the cuts. Advice, anyone?