How would you prevent a restaurant from reporting all of their competitors?

What happens when a restaurant subpoenas you for the personal details of someone who posted a derogatory report?

I find kmort's suggestion interesting - using Twitter (i.e., data that is already public) could be a smart move, as you would then be simply displaying the data rather than compiling/publishing it yourself - this could reduce your legal liability when (not if!) a restaurant wishes to defend themselves against a report.