[RyanN]

You can if you want to, but I don't see the point. Typically they are hooked up to a 20A breaker, which is way too much current to let go through the fan is something bad happens. Really, I think the fans are rated at like 1.5A max or even less. I would typically go a little above like maybe 1/2A or 1A above the fan's rating because of spike currents needed to start the fan.

The fan voltage is 12VDC.
The fan current is around 1.5A or 1500mA.

A 30A breaker will work fine as long as nothing goes wrong. Remember a breaker is designed to "break" the flow of electricity if the current goes above 30A. Seeing that the fan in no way is supposed to draw 30A of power, the purpose of the breaker would be defeated.