No one knows what SIDS is caused by, but that certainly doesn't mean your pediatrician can't have any useful info on it.
There are many studies on what reduces the occurrence. For example, the "back to sleep" campaign saw SIDS incidence go down by 50% in just a few years. http://en.wikipedia.org/wiki/Back_to_Sleep
True but that would usually be info you could just pick up from any book. The "ask your pediatrician" disclaimer just makes things seem dangerous that really aren't.
SIDS is 6x higher in families where one or both parents smoke. The lower incidence in the last years might just be because of less people smoking.
Anecdote: our midwife told us that we should put our son to sleep on his back. She also told us that in her working life, she'd first had to tell parents to put their kids to sleep on their belly, years later they were supposed to be safest on their side - there were even little foam triangles sold so the babies would stay put. Now it's on their back.
I'd still say go with what feels right and worry about things that are more important.
There are many studies on what reduces the occurrence. For example, the "back to sleep" campaign saw SIDS incidence go down by 50% in just a few years. http://en.wikipedia.org/wiki/Back_to_Sleep