Also worth pointing out that it's in Yale's interest to collect and provide the data. If they collect it, they can ensure a more representative sample size, even if they can't ensure how that data is ultimately presented. If students start using a third party service, not only does Yale still not have control over presentation, the data collected will probably make the faculty look worse by virtue of the fact that disgruntled students are more likely to respond than happy students.

As a wise man once said, "The Net interprets censorship as damage and routes around it."