Many machines, like my dell notebook, have a built in self test. On this machine I'm typing on now (Dell Inspiron 1501) if you go into the slef test mode (instructions to enable are on the spash screen) you can pick one of two tests - a quick 15 minute test or one that runs for several hours. I assume this self test is the same test that dell runs before they let a machine leave their factory. I have also seen their techs use it to determine which piece of hardware they should send you if they believe there is a hardware problem. Unfortunately, I don't think it is fool proof. I'm pretty sure the hard drive is going on this laptop even though I don't see anything to indicate that on the smart status or the self test screens. It's a good stat though.

Part of the problem may be the legal system in the US. I once ran a review site where users were allowed to post comments. In one case, I was getting a ton of negative comments posted about one particular other website. I assumed (and still do) that these comments were legitimate due to the sheer volume of different users posting them and I never edited for content. Then, I got a lawsuit for defamation. Yea, I was protected legally and won, but it costs a ton of money to defend yourself against frivolous lawsuits. The best thing for most of these retailers is probably to just not allow user submitted reviews at all which is what I do now.