Criticism in the age of internet

Some springs, I teach a college class on criticism in the age of the Internet. Early on, I ask students to think about the difference between a rating, a recommendation, a review, and a piece of criticism. Most of them locate those four types of opinion on a continuum; the earlier ones, they say, require less time to create. I ask them whether this means that they are less valid as opinions. No, they say. Definitely not. Discussion ensues. One thing they decide fairly quickly is that the validity of opinion does not mean the same thing for different types of objects. A product (a toaster or a smart phone) reveals itself immediately. The only thing you might discover about it later is that it has ceased to perform its central function well. This is not the case with works of art. They do not show themselves all at once. Rather, they unfold over time. They gestate in the minds of viewers or listeners or readers.