Definitely sounds more like the blades are hitting something rather than a knackered bearing. Could be either though.
Poke something in through the grill to stop the fan and see if the noise stops. Stopping it for a few seconds won't hurt. You might be able to manually spin the fan aswell while it's off and see what noise it makes.
If it's out of waranty I'd open it up and see if there is anything lose nearby, a wire or the plastic deflector that's just behind the fan. Otherwise it's RMA time.
Also try taking it out the case and rotating the PSU while it's on.