"Rear-ended by stupid drivers?" It's the responsibility of the merging driver to match the speed of traffic in the right lane. (Which only makes sense. After all, they were there first.)
This is something of a sore subject for me. Many drivers here in Collyfornia don't know how to merge properly. Instead of making use of the on-ramp to acceleratate to traffic speed, they'll dodder onto the freeway at 45-50 miles per hour with no regard to the speed of the traffic that's bearing down on them. That has the effect of conditioning people to avoid the right lane, which increases traffic density in the remaining lanes.
(Then there's the way the right lane keeps disappearing due to lane merges and its becoming an exit-only lane, but that's a gripe for another day.)
Geoff