For capturing the speed is not needed, you 're right on that. But for game-videorecording it's a big plus if you want to record gameplay while playing for example. I use fraps (full version) for that and record gaming action at 40 to 60 fps (1600 x 1200) which produces enormous files, because fraps just screendumps to AVI. If I record half an hour of gaming I get about 80-90 GB of footage. Slow harddiskperformance, clogging up the computer, screws up your game and make the video worthless, because of shitty gaming due to harddisklag, or because you gotta turn down quality-settings to improve performance.

I do regular backing up of my material. I keep my DV videotapes stored well too, so I 'm not that worried on loosing things that are only on my computer.