Yep, it is safe to say I was cursing Facebook yesterday - my phone wouldn't even come out of the reboot stage.
For those of you where the hard reset still doesn't help, hook your iPhone up to iTunes and do the usual you would do for a hard rest (hold the power and home button at the same time). If your phone is in reboot mode, it won't be recognised by iTunes but don't worry. When the screen goes blank, release the power button only while still holding the home button. This will force the phone into recovery mode at which point it will be detected by iTunes. Once detected, release the home button.
You will then have the option to restore.