I think this is part of the reason I actually very much appreciate the comments section on HN. Not for negativity, but because often the top comment is a good summation of the caveats to whatever's behind a given link. People selling products are not wont to tell me why their product might not be as great as it seems, unless required to by law. Even then, only in tiny print.

I'm certainly not an expert in many areas (Lasers for one), including many of the areas that these products pop up in, so when something seems too good to be true (or if I happen to have said expertise) the first thing I do is hop over to comments to see what the rest of the community has to say.

I always try to take both links and comments with a grain of salt and a healthy dose of skepticism and try to come to my own conclusions. That's not easy to do if I only get one side of the story and I don't happen to have years of experience in the relevant fields.