Yep. and while I'm generally against meddling lawyers and all...THIS is one online app I'd like to see crucified by the legal types out there.
To play devil's advocate, what's the legal basis for "crucifying" an app like this? Random people already have the ability to review anyone without their consent. To my knowledge, there's no law that prevents me from starting my own personal website and publishing my personal opinions about you or anyone else I might care to "review".
If what I say is untrue or grounds for harassment there are already laws in place to deal with that (as the GP suggested, that's what libel laws are for), but you would (as far as I understand such things) have to sue me for making the untrue statement and not my web host for enabling me to distribute it.
I don't think this app is a particularly good idea. But I don't think it can be a priori outlawed without falling afoul of free speech considerations.