My LBS has a big sign at the front of their service bay, announcing that they will not repair "department store" bikes. I was talking to one of the mechanics when a couple came in with 2 beat up Huffys. One had a bent pedal, the other a flat tire. The mechanic said "I can sell you the parts to fix the bikes, but I cannot do the repair."
You could see that it pained the mechanic, as his primary instinct is to throw the bike on the stand and fix it. He would if he could...but the directive had come down.
It's an insurance and liability issue.
As for me...if I had $1800 to plunk down on a 26 pound "carbon" bike from Wal-Mart, I would hope I would know better to take that $1800 and go to a LBS and get a bike that can be serviced and repaired, if necessary, by someone more knowledgeable than me - or the 17 year old behind the cash register.