I'd heard of this stuff before and had the impression that there was nothing there, but when I saw new allegations popping out all over in the past few days, I thought that there was some new smoking gun and I might have actually been misled all along by an honest-to-God gigantic US government/industry/CDC conspiracy to suppress the true cause of autism (with the usual disaster-movie "we don't want a panic" justification). But, especially knowing what I know about how scientific communities work, the claims were sufficiently extraordinary that I had reservations, as did the always fiercely rationalist PZ Myers, who fired off a note to medical researcher "Orac" who apparently knows quite a bit about this.
I'm not an expert, but Orac's debunking (which links to earlier writings), together with some of the comments, is pretty convincing to me: most significantly, autism rates aren't any different in countries where thimerosal was never used (strange if thimerosal is responsible for almost all autism in the US, as the claims seem to imply), and there was a similar vaccine hysteria in Britain over autism supposedly being caused by MMR vaccine that didn't even use thimerosal. There is no new scientific smoking gun, just the same irreproducible results. Aside from opponents of child vaccination and expert witnesses for plaintiffs, the claims are pushed heavily by people promoting chelation therapy for autism, which is, to put it mildly, scientifically questionable. Note also that thimerosal has been phased out in the US recently, so vaccines your kids would get today don't use it anyway. Props to Lindsey Beyerstein for also showing sense (while refusing to let Bill Frist off the hook entirely, which is probably wise; he is cozy with the pharmaceutical industry).
Orac got a lot of outraged comments from parents of autistic children, some of whom claim good results from chelation therapy. I can only imagine what they must be going through, and I can sympathize with the notion that direct experience bringing up a child trumps any quantity of epidemiological statistics. It doesn't make it true.
I have great fun bashing conservative opinionmakers and politicians for endorsing pseudoscience that seems ideologically congenial to them, on subjects such as evolution and the environment. As far as I can tell, this time some liberals got it wrong. Teresa Nielsen Hayden famously said "I deeply resent the way this administration makes me feel like a nutbar conspiracy theorist." I can sympathize, and the administration and its friends in Congress have also irritatingly frequently tried to portray reasonable opponents as nutbar conspiracy theorists. But an important proviso is that this is no excuse to actually think like a nutbar conspiracy theorist.
See also: Skeptico on the complete transcript of the conference where the coverup was supposedly hatched.