It is actually dangerous. Sorry to keep going on about mental health, but what if I looked up my doctor and there was a bad review? Then the next day he came out and recommended a medication that I didn't really want to take, but would be best for me? That bad review might be enough to weigh my opinion falsely against taking the medication - atm I trust my doctor enough so that I can refuse a medication and he will respect that, but if he really insists, I will take it as I trust that he will do what is best. If I read a bad review, I would be more likely to say I will take the medication and hide it or whatever, which is pretty much a recipe for getting sectioned.
The feedback on medical things on MN is more general - eg someone might say "be careful about just taking what medication a dr gives you", which is a totally different thing to "be careful what medication dr x gives you, he always lies and he sectioned me for no good reason" Don't you see?
Same with physical health - if I had, as said above, a verruca, but I thought it was foot cancer, and my GP examined me and told me it was a verruca, unless things developed somehow, I would trust her. If I had read a review on that site, I might think it was still cancer, get all wound up and end up being taken in by some quack or harrassing the doctor, or getting really worried and ended up with stress related illness.
This is a dangerous partnership. We mostly know we can find reviews of doctors online, we hopefully all know to ignore them. This link gives them an air of legitimacy - we trust MN.
I like MN because it has a good tradition of being skeptical and intelligent. If this carries on, I might as well be on Bounty.