I bought a powered USB hub from Maplin, just something cheap, but the guy assured me that it would work fine.
Anyway, plugging it into the raspberry pi (with the microusb power lead out of the rPi) powers on the rPi.
Will this cause any damage to the rPi? It seems to work fine with it plugged in this way (I believe - but don't quote me - that I have one of the newer rPi's, something about something in the USB has been replace with something else, I don't know).
Can you overpower the rPi? I've read loads about underpowering the pi, but nothing about overpowering it. e.g. If I use a 5.2v 2amp power lead? Or perhaps two power inputs (one from the hub via the USB and one into the microusb port.)
If its plugged into the hub twice it seems to work fine. But if its plugged into the hub via the USB port and into the mains via the microusb port then it seems to be jerky and unresponsive.