Good conversation and points.
The ironic thing about this is that much of the technology that BPL has its roots in was pioneered or heavily experimented with by radio amateurs in the 70s and 80s. I mean, much of the early technology and concepts that helped create the internet stemmed from packet radio and even radio teletype way back in the 40s and 50s..
I agree that there will always be legitimate spectrum for experimentation and recreational use, but the radio amateur hobby is very broad in scope and interests and certain bands are suitable for certain techniques while others are not, and the bands that are most at risk as far as the FCC reassigning them are the higher frequency bands that digital systems covet. A lot of commercial interests and big money salivating for more real estate. While I'm not a big user of those frequencies and never was except when I had only Technician privelages, I am all for protecting them. Actually, I take that back, one of my favorite bands is 6 meters (50Mhz) and it is just on the borderline of useability by localized commercial entities. It is the inbetween band because long distance communication is very sporadic (called sporadic E in fact) and instances of local users being interfered with by E signals is rare. But this is the fun of the band, I think. Many 6 meter enthusiasts literally sit near a computer and wait for spotters to announce an E opening when conditions are favorable. One old timey technique is to monitor broadcast television for ghost stations that pop up on locally unoccupied channels. I wonder if the end of analogue means that technique is nullified? I suppose it does because digital signals are either there or not, no snow.