Not for a single second do I believe that autism is caused by TV. Autism has clear implications as being genetic.. and so does ADHD by the way. Not to say that there aren't environmental factors that might help a genetic issue to manifest...but there has to be a predisposition in that child's genetics for it to manifest.
If anything, I would imagine TV would cause a child to hyperfocus...not have a short attention span.
I think that background noise from a TV is okay. I think limited TV watching is okay. I think sitting your baby or any child for that matter in front of a TV as a form of babysitting for long periods of times (hours and hours) is probably not very good for any child. But neither is them being on these damn computers, cell phones, and video consoles either.
I totally agree regarding autism. I just added that one in there as it's just an alternative view point. Although, if people are worried about autism and the MMR vaccine, even though there's no proven link between the 2, people may want to reconsider allowing TV viewing too. If we're talking risk factors, surely if you were worried, you'd want to eliminate as many a possible?
I disagree about it being ok to have a TV on in the background. The research backs this up as well - sitting and watching a show in detail together and discussing it is better than having it on all the time. The constant noise encourages less conversations, as well as having potentially detrimental impacts on attention span.