EDIT: An additional requirement (forgot): an external display must be attached. I'm doing some testing with my 2011 MacBook Air that is still running Lion.
CORRECTION: My MacBook Air is running Lion, not Snow Leopard. Brain fart!
Basically, if the key sensors can be jiggled closed, the lid sensor can be jiggled open. And because these happen for the same reason at the same time, that's not a two-point failure mode; it's something you'd expect to happen.
They later solved this in a firmware update, but still, first-generation Apple products are usually best to be avoided.
There are exceptions, of course. For example, I've heard of no major defects in the 1st gen iPad.
Sure, some apps don't scale their resolution for the screen yet. Photoshop is the biggest problem for me but isn't a deal breaker since I don't spend that much time in PS.
As for the OP's problem, I've never experienced it. Keep in mind he didn't say it was a retina model. I ride a motorcycle with my laptop on my back every day. It gets bounced around and jostled a lot. I've been on 4 flights with it. I've never had it turn on when closed.
Still, not very frontpage worthy IMO.
I only started noticing it after the Mountain Lion upgrade, so I figured it was more likely something to do with their crazy new sleep mode, but hey, perhaps it's a combination of factors?
IF (internal_keyboard_button_pressed && screen_closed) IGNORE
http://en.wikipedia.org/wiki/Sudden_Motion_Sensor
I suspect that the author of that blog may be seeing the same thing and it has nothing to do with keyboard problems.
These sorts of functional failure may indicate a weakness in Apple's design process and one which Apple may have trouble addressing without changing the relationship between marketing strategy and product development.
I've had a few applications (Evernote being one of them from time to time) that prevents my rMBP from sleeping. Maybe there's something related?
For instance, sometimes the screen just won't shut off when trying to put it to sleep - Closing the lid and the screen/logo stay lit up indefinitely. Chrome and the integrated graphics card really don't play well together - it's caused an OS reboot 10's of times in the past month. Mostly, waking the computer from sleep takes a fraction of a second but sometimes it takes ~20 seconds to show the screen.
I would guess that all of these are related to the integrated Intel graphics chip firmware/drivers being not quite baked.
BUT - in spite of all of that, this is without question the best laptop I've ever owned. It's also the first laptop where I haven't wanted or needed to use my iMac anymore. It really is finally a true "desktop replacement" that is totally portable. And I could never go back.
I've seen this as well, and it feels related to whether the computer is suspended to RAM (sleep) or suspended to disk (hibernate).
I think the point is that when the computer is powered off and the lid is closed, there is absolutely no reason it should ever power on by itself.
Maybe I'm overstating the variability in MBP users, but I hope you get my point.