Online rating systems are ubiquitous and powerful. But not everything is easy to rate. Restaurants and hotels are pretty easy, in part because the people rating them are consumers who are simply supplying their impressions and opinions. In these scenarios, everyone who rates and comments is equally (un)informed. People know what they know and think what they think and rate accordingly. The value tends not to be in the individual comments (trust me, I've read more than my fair share!) but rather,...