In the last week I've added 1,400 miles to my odometer. It's hard to drive 5 miles without encountering someone attempting a boneheaded maneuver, or has learned horrible habits from other poorly trained drivers. My recent trip was full of encounters with these people.
Of the ill considered practices that I encountered, none was more prevalent nor more annoying than when a driver accelerates as a vehicle that was traveling faster attempts to pass. I witnessed this over and over, sometimes I was in the faster vehicle, sometimes it was someone else, sometimes the faster vehicle managed to pass, others the slower vehicle accelerated enough or cut off the faster. It was a plague throughout Pennsylvania and Ohio.
The worst part about this is that it doesn't make any sense. If someone is going faster than you, and wants to continue going faster than you, why would you take actions to ensure that they cannot go past you? The safest thing to do is to allow that person to pass.
At the very least, do not slow back down. The only reason I can fathom for that action is to tell the other person that you think they're going too fast. That's not your job, unless you happen to be a member of the police with jurisdiction over that stretch of road. If someone is really going that fast then the safest action is to stay out of their way, keep your eyes open, and hope that they can speed along on their merry way. Getting in front of these people to slow them down only incites them to take dangerous actions to try to overtake you.
I understand a few scenarios for this behavior, and in some cases it's justified. If the faster person will have to make a dangerous maneuver to pass you then it's acceptable to either slow down or speed up a bit to force them to pass you later. Another scenario is when you're attempting to save gas and effort by using cruise control, then this other person is not passing you fast enough, so you have to get in front of them to maintain your speed. You should weigh the difference in speed that you would have to decrease due to them versus the amount of speed you would cause them to decrease by getting in front of them. As soon as you possibly can you should get to the right to let the other person pass. If you just decided that you want to go faster, wait until they pass or at least try not to slow them down. There are extenuating circumstances for everything, and if you're courteous then other drivers should appreciate that you tried.
The only other way that I can make sense of this behavior is libido, in the form of a belief of entitlement and boy-racer machismo. These are just wrong. If you think you are more entitled to any piece of public road than the next person, I'd love to hear why. I'd also love hear how you know that they are less entitled. Keep in mind that many states have laws stating that you should keep right except to pass and some even require that you yield to faster traffic, with no mention of speed limit.
There's really nothing worse than boy-racer machismo. It's always funny to see the hypocrisy when someone pulls a boy-racer maneuver to try to thwart a boy-racer. You can't sink to another's level and then try to act better than they are. It doesn't work that way. If you turn someone else's desire to pass you into a drag race then you're not just being stupid, you're being ridiculous. You're encouraging them to do something dangerous, and thus endangering yourself and innocent bystanders.