Originally Posted by ACDC ROX
Wow, what an informed comment....
Anyway, I've found it best to use a combination of both. Now, one of the biggest arguments against eBay as you can see is that it's easy to be scammed. eBay provided protection against this though. Also, make sure to pay with PayPal - they've worked with me on several transactions gone awry. For example, I purchased a Sin City poster that was claimed to be an actual promotional copy. When I got it, I found that it was actually a reprint. I filed a complaint, and PayPal gave me my money back. Long story short, I've had nothing but positive experience with eBay and PayPal customer protection and eBay as a whole (I love it!).
Now when I built my computer, I made sure to buy certain parts new. One thing that I'd never buy used (unless it came from a very reliable source) is a hard drive. They are fragile pieces of equipment, and I feel much better just buying it straight from Newegg. Another part that I prefer to buy new is the processor. Removing a thermal pad is much easier when it hasn't been used yet, and a lot of processors sold on eBay do not even include the fan. This may or may not be a good thing depending on what type of cooling you're looking for, but in this case, it's more of a personal preference (as opposed to the hard drive).
Now, for things like RAM, video/sound cards, power supplies, and optical drives - definitely go eBay. You can find these things much cheaper and in great condition. It's not as easy as point and click though. I spent at least a couple weeks scouting parts on eBay. It will take you some time to find the best deals on the parts you want, so if you're in a rush, it would be better just to buy everything from Newegg. Otherwise, take your time, and save some green!