In Texas, as others mentioned, the left lane is for passing only. By hanging out in the left lane, not only are you causing congestion and making everybody's commute longer but you are creating a hazard and breaking the traffic code. The difference between you and the speeder is, on most roads in Texas, the posted speed limit is not a maximum limit. It is the recommended limit under perfect driving conditions. That doesn't mean people can't drive faster and not break the law. However, it is always a violation of the traffic code to drive in the left lane when not passing.
To clarify: driving over the posted limit sometimes is within the law, what you do is never legal.
Moreover, it's just a ******* thing to do. Yes, sometimes people speed just because they enjoy driving fast, they drive like a-holes, etc. but there's no way for you to differentiate between that person and somebody who's speeding because they are late to something really important, possibly of no fault of their own, or on the way to the hospital.