I was talking to some guys last fall at a PA produce auction who were doing hauling for farmers and buyers. They told me things had changed earlier in the the year (2010) with regard to DOT.
I found this link to a trucking article about it:
Pennsylvania carriers must display DOT number | Overdrive - Owner Operators Trucking Magazine
Also in years past I recall that PA did not require the numbers for intrastate. But when I looked at FMCSA they now show PA as one of the states requiring registration. Who knows, they may even be down to 10,000 lbs like the other 28 states.
NY started this a few years ago, but they gave warnings at first; my friend got stopped by NYSP for a warning with his F450 but now I am seeing DOT numbers on 2500's and even F150's pulling trailers. For anyone operating in PA like Builder, they should probably try to keep up with what's going on and how it's being enforced.
Yup I had read that article but haven't seen anything else about it so didn't know if it was in force yet or not.