SeatCounter uses screenscraping technology and scripts to pull information from airline web sites. Great tool, but only as accurate as the information the airlines provide to the public.
The person with the family member in the business is absolutely correct. One of my wife's clients, before she retired from UA, was a senior CSR and could provide all that information in real time. She was, and still is, an "angel" (which is what we affectionately call such employees willing to help us out). Mileage running depends on accurate GDS/CRS data and I pay quite handsomely for what I get, but it's still not as much as an airline employee has.
Yup, SeatGuru (and SeatExpert) are fabulous for telling one about where they might wish to sit on the plane but that's it. Great tool, though. I annotate my hardcopy UA elite seating charts with SG notes so I can refer to them when angling for seat assignments on rebookings at the airport or on the phone (away from the computer).
Pat