With all due respect Mr. Barry B, the pilot of the "ultralight" you saw likely broke no rules whatsoever, however has displayed poor airmanship.
Under the current 95.55 regulations there are no restrictions on flying below 500ft over private property, unlike GA flying where you would need permission and an appropriate low level endorsement.
If you can get me an aircraft type and possibly a colour I can likely tell you who was piloting the aircraft and I can have a word in their ear or make further enquiries, however little action could be taken unless written statements were prepared and the author prepared to go to court.
But don't despair! When the part 103 gets approved there will be no operations below 500ft unless taking off or landing or with an appropriate low level endorsement.
As you say, similar to the happenings less than 50 miles away at 8:40am. The 172 aircraft had performed the stunt many times before but not in the area where the power lines were located and the area had not been surveyed by the pilot. How many times have others done something similar and had a close call? More of us that we would like to think no doubt!