Here's one I found: http://www.medicinenet.com/script/ma...ticlekey=78008

Basically, you shouldn't keep your baby in the infant car seat (or swing or bouncer, for that matter) for extended periods of time. In addition to the problems noted above, it's also a factor in positional plagiocephaly (the head flattens due to the amount of time spent in that position).

I tend to think these concerns are more for the parents who bring their baby in and let it sleep all night in the car seat because they're afraid to wake it up to take it out. As long as you don't leave the baby in the car seat for hours on end, it's probably fine. I kept my son in the car seat while running errands, grocery shopping, going to the mall, but it was never for all that long. He had to come out so I could nurse or change his diaper while we were still out, and he never stayed asleep while we were bringing him in the house.