I was browsing around, and to my suprise, the PSP's defects have been slash dotted! After viewing the site in question, I was suprised to find out that one such defect is actually intentional!
Take a look at
This Picture and take note of the red lines which show how all the buttons, and their actual contacts line up. If you look at the Square button, ([]), you'll notice that it's barely over it's contact, and if depressed, would never cover more than 50% of the contact.
This design flaw has been associated to the Square button's problem of becoming stuck as well.
Now, add this problem on top of the already known problems of air bubbles in the screen, dead pixels coming in threes, analog nub not really being analog, analog not working, nub falling off, psp powering on but not starting, flying umds, and you start to wonder, why hasn't Sony made a press release on this yet?
Nintendo made a press release about DS' dead pixels within the week of launch, if not by just a day or two. I guess this goes to prove that one company is after your money, while the other is out to give you exactly what you've paid for. I'll let you decide which is which.
If you'd like to read more about the PSP's defects, you can find the original article
Here.