Buying ANY hard drive is a gamble. For some people, one brand/model will crash, while for others they work perfectly for years on end. After hearing IBM (deskstar) drives worked well for many users about a year ago, we bought 10 120GB models for storage. So far, 2 have since stopped working. So that's an 80% success rate so far (only time will tell if that number drops).
As for data integrity, you might want to look into RAID arrays. The proper setup will allow you to allways be able to recover your data (except in the most extreme of cases). I'm not going to go in depth about what sort of RAID configuration is best, etc. here, so just do some googling on RAID arrays and find out if you're willing to shell out for it.
I'm all for keeping it simple, and am leery of RAID for that reason.
For DV work, ANY drive made in the past couple of years will work fine. Disk drive performance is now many times better than the 4GB drive on my first DV editing system (a Compaq back in 1998), and even that drive could do DV streaming without dropped frames.
I've captured and edited on laptops with with 4200 rpm drives. 5400 rpm works fine. However, these days there is no reason to get anything other than 7200 rpm.
I have nine computers at my house, plus I've run several software companies. I've only had one disk failure here since 1985, and that was due to overheating. Of course, they do fail, but most major brands (IBM, Seagate/Conner, and WD) are all going to be fine.
The only really important advice is: get a BIG drive. I got two 120 Gbyte drives in the computer I purchased last fall. If I were to get another computer now, I'd get two 240 Gbyte drives. I sometimes have three cameras going, and it is great to be able to have all the footage from all the cameras available, at full resolution.