/rant ON
This is yet another reason why I get frustrated with people that expect CarFax to be the definitive answer to whether to buy a specific vehicle.
Not all accidents result in damage that will be noted in records maintained by official sources. Not all payouts for damage will be from insurance companies that pay to be part of a large mainframe data dump. The CarFax section on accident damage talks about MAJOR accident damage...to me I would read that as being something beyond run of the mill fender-bender.
I look at this question as being yet another area where people ought to re-evaluate some of what they take as gospel...like with the odometer rollback question from a few weeks ago on a Miata site- the only odometer records I would consider official are those that go with a title transfer. There is an increased likelihood of entry error if you relay on the smog check people to key it in annually. In the instance that came up, there was a series of entries that went from 28,xxx to 78,xxx back to the reading on the car that was in the low 30's...my guess is that the 78 was a typo because of the relative proximity of the dates.
Is it a good tool? Absolutely. Should it be definitive? NO! It provides the basis upon which some investigation may be necessary if you have questions.
/rant OFF