I prefer definitive answers to wild speculation and off topic meanderings, and since my macbook was also plagued by this mysterious non-responsive click at the top of the trackpad I felt the need to get some answers.
So, is the whole trackpad supposed to click in the first place? Well, Apple's says:
"All-new, smooth glass Multi-Touch trackpad.It’s redesigned with even more room for even more gestures. Now the entire glass trackpad is also the button, so it’s clickable everywhere." (see apple.com/macbook )
And further:"The amazing new trackpad doubles as a button — just press down anywhere and consider it clicked." (see apple.com/macbook/features )
Admittedly Apple has taken a somewhat different stance here:
http://support.apple.com/kb/HT3211 where they say "Unlike typical trackpads, this MacBook and MacBook Pro trackpad is a button in itself; you can click almost anywhere on the trackpad."
With this information in hand I took my Macbook back to my local apple store (toronto eaton centre). At first I was greeted with much distain. "No", they "told me, you are not supposed to be able to click at the top of the trackpad".
"To which I replied but what about this information on the website?" I said.
"Oh well, you can TAP anywhere, but the trackpad is not clickable everywhere" They said.
Of course I pointed out that this is not how the website describes the features, so this turned into a bit of a discussion. Mac "geniuses" became involved, a manager at the store... The decision: "Store-wide, the top of the trackpad is not supposed to be clickable" (not his exact words, but something to that effect).
To be fair the employees did allow me to exchange my macbook, subject to the fact that I would have to pay a restocking fee if i opened it and wanted to return it again.
Feeling a bit worried (from reading these forums) that my replacement macbook would also suffer from the same defect, I felt I needed to reconcile the difference between the store's position and whoever writes the words on apple.com/macbook.
I called the store again, spoke to a manager, tried to get an explanation as to how they could take a position that was different from what the website reported, and is this a manufacturing defect or is the machine simply not supposed to be clickable at the top of the trackpad. The store stuck to their position that the machine is not designed to be clickable at the top of the trackpad, but hey, we understand your confusion, if you have to return it, we wont charge you the restocking fee, even if its opened.
Happier about the fee, but still unsatisfied, I called the folks at apple care. They would know the answer, right?
After communicating the above information, the apple care tech took some time to review the materials provided by Apple and confirmed that indeed the tackpad SHOULD register a click at the top, and if it does not, there is a problem. He was bemuddled by the position of the Toronto Eaton Centre Store, but assured me that if my new machine had the same problem, it could be returned or exchanged.
That's my report on the issue, take what you will from it. Hopefully this answers some questions or concerns. For myself, I'm still debating if I should wait for that second revision of the Macbooks sometime next year, given this issue.