"passing on the right" only happens when YOU are screwing up....
A couple exceptions:
1) If we are all in a left-turn lane and get a left-turn signal onto a 2 lane road. Legally I make the left into the left lane, then should change lanes to the right (rather than making a 'wide' left). Problems come up when some Speed Racer behind me follows my butt through the left, then veers around me instantly (usually still in the intersection) to overtake in the right lane. LET ME MOVE OVER! I'd be out of the way and to the right in seconds if they just give me 2 seconds!
2) Construction: On my commute for almost a year now, everyone has to merge into the left lane where the road reduces for the construction. We all line up and wait except the few arses who overtake EVERYONE waiting thier turn and then ram into the head of the line at the last second.
3) Similar to #1 above, there are a couple highway ramps around here that (stupid design) make you merge in on the left of the highway. In this case, if I'm not going fast that day (read wife and kids in car), I merge as far over to the right as quickly as I safely can, except for the couple idiots that are behind us and also merging, but they literally veer across 2 or 3 lanes in order to overtake everyone else - thereby delaying us actually getting over to the right where we should be. Give us a couple seconds to move over to the right and then the left lane is all yours!
OTHER than the above, you are pretty much correct that people who get passed on the right are almost certainly hogging the wrong freaking lane!