The Mysteries of Memory

Wow, I've had a lot of posts in the last week and on random topics. Well, here's another one--the mysteries of memory. In particular I was wondering how the brain chooses what to remember and what to forget. I'm a mediaphile, always hunting the next great movie/tv show/book/short story/etc, and I am constantly amazed at how much totally useless information I have stored up there. Is all that information using up my storage space? Is that why I forget where I put my car keys, or totally blank on test questions in my classes?

Does anyone else find they have huge amounts of totally useless things stored in their brains? For instance:

1. Video games walkthroughs. I haven't played Super Mario Bros. 3 on NES for 10 years. The last time I played through it, it had been at least 5 years before that, and I knew EXACTLY where everything was in the game. Where the warp whistles are, exactly how to get hammer brothers suits, where the invisible note blocks are. And my muscle reflex is still completely intact for that game, I barely skip a beat.
I could also probably list at least 20 special moves for various characters in the Mortal Kombat series, though I haven't played those for 10+ years also.

2. Random associations. When I was in junior high and high school, I liked to play through video games on one TV while I had the little black and white TV showing TV shows in the background. In this one, one media becomes melded together with the other in my mind. There's a particular level in The Illusion of Gaia (on SNES) where you're fighting your way through the jungle. When I was playing through that, I was watching an episode of Star Trek: The Next Generation, where they meet a genderless alien race. There's one member of the race that is intrigued by human femininity and so she tries to be more womanlike. Riker grows a love interest for her and has some very awkward conversations about sex. Then at the end, the race discovers her deviance and brainwashes her back to "normal" behavior. I haven't seen that episode since then, but I remember all those details.

3. Faces on movies/tv shows. My wife and I make a game of it when we're channel surfing or going out to movies, if we can figure out where else we've seen an actor without going to IMDB. We've been doing that so long that it's rare to watch something where there isn't some association. I should start playing Six Degrees of Kevin Bacon, that game always sounded fun when I heard it on radio shows and stuff.