In the bike shops around this great land, the toy-department bikes from K-Mart, Target, Wal Mart, and such places are commonly referred to as Bicycle Shaped Objects, or BSOs, for short. Many shops will turn away repair or maintenance work on the BSO, due to the fact that many of the parts are of non-standard pattern, and the original assembly is usually so bad that the labor to make the BSO safe to ride will cost often more than the original purchase price.
I remember working on one BSO (we didn't turn them away, out of hand) for a lady who actually rode her Roadmaster bike, a lot. It had the usual maladies of warped, non-tensioned wheels, misplaced brake levers, etc. But, she told me that she had ridden the thing for 10 or 15 miles a day, for six months, and that she really enjoyed getting back into some physical excercise in her 40s.
I fixed whatever it was that she brought it in for. Then, while I had it in the stand, I went ahead and tweaked a few things to make it work better (and more safely). Scott was a little put out that I threw in some free labor, but we were slow and no one else had to wait for a repair because of it.
When the lady picked up the bike, I pointed out the extra stuff I had done for her. She was very appreciative.
"The shop down the street said it wasn't a good enough bike to work on," she said. "They just ried to sell me a new TREK."
"If you are riding it, it's a better bike than a TREK that hangs in the garage," I replied. "Any bike that gets used is a good bike, to me."
She paid her bill, and left. A few months later, she finally recognized that the sub-par performance of the bike was interfering with her enjoyment of riding, and she came in and bought a "real" bike.
The BSO, when properly used, can become a gateway drug for bicycling. So, I try to not discourage people who ride them.