Mine was when the express lane was completely stopped (not moving for 30+ minutes), and EVERYBODY was crossing over to the local lanes through the median.
I was in a line of about 30 cars, and I saw the cop down the highway sitting there. When I pulled out he came right behind me, pulled me over, and gave me a two point ticket. I asked him why he let about 30 other cars go and singled me out. He laughed and walked away.