I usually don't immediately pass drivers ahead of me in the HOV lane that are going too slow. I've found it's necessary to observe the slowbie's habits, especially if they have tinted windows.
This afternoon, I wound up behind the stereotypical frustrating hybrid driver in the HOV lane. Couldn't maintain speed up hills. Would speed way up when someone passed on the right, then slow down again for no apparent reason. I noted a speed variation between about 80 mph and just over 55 mph.
If the driver is just slow, I just pass and don't think about it any further. But when they're inconsistent in their slowness, I keep back until I can get a car or two of cushion between my rear end and their front end.
That opportunity didn't present itself today, so I had one slow ride (except for occasional quickness) home. Eventually, the slowbie ahead of me got to the right, and I passed. I glanced over and, wouldn't you know, they were on a cell phone.
I think there is enough anecdotal evidence about the dangers of drivers on their cell phones to justify immediate vehicular detonation when they're spotted...