[This thread was split off from an earlier general one about Powered Hubs and has been given a more appropriate subject line. Note that replies prefix "Re:" to the old subject line.]
The Pi's very poor power design results in some perfectly good self-powered hubs being incompatible with it. For example, the cheap little 7-port self-powered Dynamode USB-H70-1A2.0 hub that Farnell advertises as a Pi accessory:
is not actually Pi-compatible at all, because in addition to powering its 7 host ports, it also powers the Pi board through its A-B upstream lead yet is incapable of supplying enough power to do that successfully (the Pi's Vcc drops to well below 4V). As a result, when the micro-USB is powered down but the hub is powered up and connected, the Pi ends up rebooting continuously every couple of seconds, potentially leading to destroyed HDMI displays among other worries.
So, buying a self-powered hub is not necessarily the end to your Pi power problems.
Really the Pi's power design needs to be nuked from orbit and redesigned from scratch. It's just plain bad in numerous ways.