I'll jump in here:
Dell's don't suck. ?? You get a lot of machine for the money. But, discounting all that, you get an incredible warranty.
I've been building my own machines for about 8 years and will continue to do so for the predictable future - but if you're not comfortable with building your own machine - Dell can offer some nice systems at competitive prices.
The real advantage is the software licensing (you know...if you want to be "legal" and all that) and the warranty.
If you get a DOA from most online places, you are at least responsible for the shipping costs (there and back). That's money. Plus you are often dealing with OEM parts with limited warranty or distributors that may refer you to the manufacturer. That's a pain in the donkey.
With Dell (or most other large, reputable PC makers), if it breaks - they fix it. Period. No cost to you.
Get a PC from Dell and it doesn't work? Call them and they help.
Order pieces from the Internet and it doesn't work? Sucks to be you.
My point being, ordering from a place like Dell has its advantages. It may cost a couple hundred dollars more but, for some people, there's a lot of value in that couple hundred dollars.
Don't assume there is one solution that magically fits for everyone. Building has its advantages and pre-built has its advantages.
And Gond is right on target on how places like Dell can stay in the same ballpark on price. On licensing and things like Intel processors, their multi-million dollar orders are going to drive the cost per unit down much cheaper than you can get from Internet retailers or Bob's Corner Computer Shop.