You make very good points, but anyone trying to calculate these forces would have to deal with a lot of guesses. Nokia will not release the exact details of the solder compound used, PCB preparation, soldering methods, etc. Even slight variations in any of these factors can have dramatic effects, just think of the scandal Nvidia was involved in with their G84 and G86 core video cards. A minor error in specifying the correct solder compound led to a 30% failure rate of all those video cards, with more likely to fail in the future. Nvidia themselves set aside $200 million to correct the issue, although the damage may be much higher than that. The only way to prove defects is to test these things. But you need to purchase a batch of N900s and have an independent lab test the forces required to break the USB port off. I'm guessing you'd need at least 4 units to test all cases (one for each axis, plus one for repeated straight, proper insertion and removal of the USB cable). Most likely you'd want more units for each case. So we're talking thousands of dollars just in N900s, plus fees for the lab. Not going to happen.