A person can never have a big enough hard drive. I bought a 1TB LaCie 2Big raid drive last month and it has only 450 GB left on it. At this rate, it will be full in about a month or two and I'll be buying a second one. They offer a 1.5TB drive but it is just two 750GB drives that work as one. I would love a 2TB drive!
But see, that's just nuts. Across two computers (and five hard drives), I think I use up a grand total of about 150 GB. I think about 50 GB of that is just video (DivX and avi, mostly... a few movies.. mostly TV shows). And a lot of that is redundant data! I mean, I guess not a TON, but some. If you count Photoshop CS3 Extended Mac and PC as redundant. I've also got CS2 and Photoshop 7 on this machine just... I guess because I can. I like PS7. One of my favorites. Actually... lol, I've got Photoshop 3, 5 and 6 on here too. And 5 on the PC. Granted that takes up not much space.... but still, you get the picture.
The majority is programs and whatnot.
What could you possibly be doing that needs that much space? Video work? Don't you ever get around to throwing out old stuff that you no longer need? I throw things out all the time, whether I need more space or not (which I do on my laptop's crappy 60 GB drive... one more reason I'm getting a new one soon enough..)