What if you declare it up front, in big print. Really. I wonder how many people would still stay. Just put it right above the dotted line on the front page.
By signing this receipt and accepting the key to your room you agree you not place a negative review of this facility on any public accessible site.
The fact that most people would only look at the bottom line (i.e. price) doesn't mean that this wouldn't be a gross infringement of freedom of speech, and unfair trading to boot. Trading involves the possibility of goods not being up to par, and hence the customer complaining to a third party. As long as complaints are not libellous, there is no reason why they could be forcefully restricted.
Still not a chance. Big ink, flashing letters, PA announcements. Same as invisible ink. Courts have a very low opinion of people getting "tricky".
In Germany at least, for example, ALL Click-Through licenses are invalid (last I checked).
A US company I worked for had various (illegal in Germany) data tracking stuff activated. When I pointed this out, they just pointed to the license agreement. Morons. (It was a hardware/software combination, and you only got to the software a long time after you had bought the hardware).
By signing this receipt and accepting the key to your room you agree you not place a negative review of this facility on any public accessible site.