Interesting, however I would point out that Gruber isn't reviewing the app, he's reviewing the founder's quoted claim that the app is a data collection play.

Personally, I disagree with Gruber: Facebook and Foursquare seem to be evidence that people will gladly give up their personal data in exchange for a "social" experience. But whether Gruber is right or wrong is not the point I was responding to, it's whether Gruber would hypothetically like the app if it was hypothetically bought by Apple.

This is irrelevant to what he's saying now. Even if he does like everything Apple does and does hate everything Apple doesn't do, appealing to his bias is the textbook definition of an Ad Hominem:

  An ad hominem, short for argumentum ad hominem,
  is an attempt to link the validity of a premise
  to a characteristic or belief of the opponent
  advocating the premise.

If he's wrong, we can attack his argument directly. How can we have a meaningful discussion about what he might say if some hypothetical future acquisition takes place? Worse, what if he's right now and would be wrong if he did change his mind after some hypothetical future acquisition?

In that case, dismissing him because of his bias might rob us of a valuable insight.