A vacuum cleaner is not a reversible transducer, due to turbulence or something.  I think it's similar to the feynmann story about sprinklers in swimming pools.

Oh, and vacuum cleaner motors are universal motors, which don't make very good generators.  You generally want either an externally excited motor, a permanent magnet motor, or a synchronous AC motor for good generation capacity.  These are more expensive.

And then there is synchonisation with the grid, stability, remote control, self protection in high winds, abrasion (the vacuum cleaner turbine is in a dust free environment - I once tried to use my mum's vacuum cleaner without the bag, with a second pipe from the blow hole out the window.  It lasted about 5 minutes before it seized up.)