Here's my letter, for what its worth:

I am writing to ask you not to allow the implementation of BPL
(Broadband over Power Lines) in our nation's communities.

I rely on shortwave radio as a source of entertainment, world news and
cultural information. I listen to low & high-power broadcasts from the
world over. Reliable reception is already a challenge due to the
interference caused by the deplorable state of our nation's power
lines. I have had to send several complaints to my local power company
due to electrical power pole arcing that interferes with my shortwave
radio. Adding broadband data to these already unreliable power lines
would render a bad situation worse. In my experience, power companies
have little regard for complaints regarding radio interference, and
are slow to respond, if at all. I consider it irresponsible to entrust
BPL technology to power companies that already have an indifferent,
monopolistic attitude towards customer service.
Power companies are also overwhelmed with maintaining the poor repair
state of their equipment. With the addition of BPL,
how will power companies manage to stay within the radio interference
regulations set forth by the FCC?

I beleive BPL would be an unreliable system of delivery, and an
unneeded duplication of existing data services. It would interfere
with all shortwave radio services, including commercial, utility,
aircraft, rescue, and amateur radio services. Its effect on higher
frequency services due to harmonic interference remains to be seen.

In all, I think BPL is a unrequired, unpredictable technology and I
urge you to prevent BPL from polluting our nation's radio spectrum.