I guess I just don't see the point of requiring a user account if it isn't adding value to either the user or the app creator.
One more reason not to use Facebook as a login mechanism I guess.
As a programmer, I surely hope you don't think the only purpose of user accounts is to gain personal information.
Hacker News does not ask for personal information. Does that mean we shouldn't have to log in on HN?
I think he's looking at it from a product/sales lead perspective. HN isn't trying to sell us anything.
It adds plenty of value for the user: they get a logon to the app which allows them to keep information across sessions, while not providing the app vendor any information unnecessary to that function.
It provides a authentication as the same person without providing identification of who that person is.
Now, obviously, anonymous login provides less value to app developers who are using using logins to harvest personal information from users, but then, that's a plus for users.
Specifically, he wants some contact information so he can follow up with a lead, which I think is reasonable. Your average customer may not have time to put much effort into a product/service search and a (relevant, informative) follow-up email can be very helpful.
Ideally you do want what's best for the user, but if more revenue is coming in from the old, non-anonymous method, adoption of this one may be slow or limited.
Now if the app creator has a way to push a message back to the user (fb message or something) without knowing who they are, that might be a good compromise.
Logging in to a site provides more value than just sharing personal information. For me, I rarely, if ever, want a site to know my personal information. That's why I rarely use Facebook login service. Now I will.