I had a carfax account for a month. It's really not that useful. If there is any major things, like the car being totalled or something, that will show up. Most accidents won't be on there. I'm assuming it's only if you get money from the insurance companies and they record it (police don't take VIN's so I'm assuming that would come from insurance companies).

I ran 80 reports and then it complained and said I had to contact them to prove I wasn't using the account commercially and it was actualy me using it. I never did and just let it run out.

The few things it caught. One had an inspection with 120 miles, then a later inspection where it only had 80k (probably odo fraud) and a few had reports reported. About 85% I'd say were clean. Seeya.