A few years ago I was on the interstate, driving about 65mph. A 45ft DP passed me doing about 75, he was pulling a large enclosed black trailer that had a large silver Mercedes emblem on the back.
After about a mile the DP slowed down to about 60mph, I eventually caught up and passed him courteously using my signals and allowing plenty of room before changing lanes. About a mile down the road the DP sped up and passed me again. Again, about a mile down the road he slowed again, again I passed him.
After about a mile here he came again, this is when I gave him a big, and quite vigorous one fingered wave. He disappeared over the horizon when he passed this time.
I truly believe in Karma and my belief was justified about 30-40 miles later, the DP was pulled over on the shoulder with a flat on his trailer, and it was just starting to rain!!!