rephlex writes: Along with the ameliorated but still ongoing problems with USB on the Raspberry Pi it appears that the number of Raspberry Pi's shipped faulty appears to have significantly increased in the last month or so with one report on the forums from someone who claims that they recently received three faulty Pi's out of ten and another from a person who claims both of theirs are faulty. These reports have been described by Raspberry Pi Foundation representative who posts on their forums as jamesh as "statistically insignificant". This is the same person who incorrectly claimed in August that the Raspberry Pi was still in beta. There have also been recent reports of poor packaging with the damaged PCB unsecured and rattling around inside, solder bridges between header pins causing constant rebooting as well as multiple instances where PCB holes have been inconsistently filled with solder. See here:
rephlex writes: The USB controller used in the Broadcom BCM2835 (which is the SoC the Raspberry Pi uses) has buggy drivers which have been causing problems for many of its users. In addition to this the Pi can only supply an unusually low amount of current to its USB devices, just 140 mA approximately, and using a powered hub to sidestep this limit exacerbates the issues caused by the USB drivers. Even Ethernet is affected as the Ethernet controller used on the Raspberry Pi is connected to the SoC via USB. This has resulted in packet loss and even total loss of network connectivity in certain situations, see https://github.com/raspberrypi/linux/issues/29. Attempts have been made in the past to fix the buggy USB drivers as there are other devices which use this problematic controller. None of these attempts seem to have achieved very much.
rephlex writes: "There are multiple Raspberry Pi users on the official Troubleshooting forum experiencing hardware problems with their Pi. It appears the Raspberry Pi has problems with USB, specifically with powering peripherals that require 140 mA or more. That situation causes a voltage drop that results in the USB voltage becoming out of specification. This has resulted in malfunctions with USB devices such as Wi-Fi dongles, even when connected to the Pi via a powered hub. Also, there appears to be Ethernet problems caused by this "excessive" (but well within USB specifications) current draw: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=6&t=6037"