I had an argument with my wife recently about this, and I lost. We were driving on TX 183 headed south. She had the cruise set on 70 and was in the left lane, camping out. Other cars were continually passing her on the right, several honking or flashing lights. I finally could keep my peace no more and asked her to move over.
She said the left lane was safer (?) and she was more comfortable there and the law only required her to stay in the right lane if there was a sign that said "slower traffic keep right", which there wasn't.
I called BS. I was actually wrong.
Here's the breakdown of "keep right" laws. In Texas, not only is it fine and dandy to camp out in the left lane as long as you're doing the limit, unless there's a sign that says otherwise (to be fair I have seen them, mostly on rural highways), but it's also illegal to pass on the right, so by the letter of the law, if you are doing so and someone moves around and passes on your right, THEY are breaking the law, not you. Legally it seems they should wait for a broken line and pass on the left. Correct me if my interpretation of the law is flawed here.
EDIT: After reading the actual statute, it's fine. The no passing on the right applies to shoulders only.
Anyway, for your discussion...