Many experts agree with you. Facebook disagrees for this specific instance. They advise developers not to ask for more permissions than they need, because the more permissions you ask for, the fewer signups you'll get. That suggests that a non-trivial number of users are reading something on these particular dialog boxes.
Non-trivial is a large number for Facebook. They nerfed their "Friend Lists" feature because only 5% of their userbase, i.e. 25 million people, were using it.
It doesn't suggest that to me. It suggests to me that they would prefer you not ask for too many permissions because they've learned from Farmville that overbearing apps get bad PR for Facebook, and the fact that some number (perhaps quite trivial) of people will be turned off by it is a convenient disincentive.
I guarantee you I'd get 80% conversion to "Format C:/ and pillage your Googles" if it were the last step of the BCC instller.