There is still a lot of debate in the medical community as to whether there is an increase in autism itself, or whether we have just gotten better at identifying it, thus the rising rates of diagnosis.
Yes, that has been part of the debate....in my case, I personally know of 3 people dealing with an autistic child. Prior to 5 years ago, I didn't know any. It sure 'seems' like there has been an increase over the last 5 years or so. Also, I think it is Congressman Dan Burton that has an autistic grandchild and has been trying to get more information on the topic brought forward. Vaccines made now have decreased levels or in some cases eliminated the thimersol (mercury derrivative), that was in previous vaccines. There has been some debate that some children were more 'genetically' susceptible to the thimersol.
Anyway, still an unfortunate condition no matter the cause, and sad to deal with when it affects your family.