Carfax is a TOOL, just like your eyes, knowledge and experience. Even the carfax commercials here if FL with their little fox mascot says they can't know EVERYTHING about a car, but it's a good place to start for info.
If you are looking to purchase a preowned car and think you can rely on any ONE
source, then you obviously don't really care what kind of car you're getting OR you're just plain lazy. Buying a car is just like any other high dollar purchase, YOU HAVE TO DO YOUR HOMEWORK!!!
When I have purchased preowned cars in the past I have always used carfax, but not solely for an accident history. I like to know how many owners a car has had, I also like to know where they come from. Personally I won't buy a preowned car that has spent any time in the snow. Carfax is a great source for that information. Knowing what parts on your car were replaced under warranty is also a good piece of info to have.
Back when i was looking at buying a CLK55 I noticed that many of the cars I was carfaxing had numerous third brake light replacements under warranty. Evidently, there was an issue that mercedes had with them blowing out prematurely. Im talking like 5-6 replacements in 3 years...and on multiple cars so it wasn't isolated.
Is there a way to beat carfax if you want to...OF COURSE there is...DUH! But thats not really the point is it?..... because THAT is where you are supposed to use OTHER TOOLS....you know as part of your basic homework before you shell out THOUSANDS of dollars