Not sure it's as simple as that -- that page says "non-relativistic" at the top, and a real doppler fan at 0.3c would be experiencing time dilation at the tips relative to the observer, so the emitted frequency in the observer's frame would be changed.

Another consideration, along the lines of tanstaafl's, would be that the energy taken to spin up a fan to that rate is of order 10^16 J (probably more as that's another non-relativistic calculation), or the difference in energy use by a CFL compared to an incandescent over 6.3 million years, so you'd have to leave it turned on a long time before it paid for itself.

And if tanstaafl had suffered catastrophic fan dissection at 0.3c, it would have essentially dumped all that energy into explosive destruction -- an amount equivalent to about 2 megatons of TNT.

Peter