I was headed home from work, and noticed the pickup who was following me. Traffic slowed and he went around. I looked over and I think he looked back and waved. Later, he slowed down and I caught up with him again. We were both looking at each other, but I couldn't tell if he was waving or flipping me off.
Unfortunately, I was at my exit and he was continuing on, so I'll never know for sure.
For future reference, if you have darkened windows, and you ARE trying to cruise someone, roll your windows down, so they can see you.