Everyone else on the road. If you want to be distracted, go do it in the right lane (or better yet, in an out of the way parking spot).
Don't piss in the commons - it's what you are doing when you hog the resources of the road.
I sort of boil down road courtesy to nearly one rule of thumb -- don't make the other guy brake.
If you're heavily speeding or sitting on someone's bumper, you're doing just that, forcing immediate manoeuvre and preventing emergency braking.
People who are not speeding may want to overtake too. They may misjudge your car's distance of you're going very fast.
Even if we were talking about close tailgating, that in no way requires the kind of instantaneous reaction required by the sorts of discourteous/dangerous moves that make the other guymgal brake. This is in fact the exact problem - oblivious idiots will happily sit in the passing lanes for many miles creating congestion and hazards. In many parts of of the EU, this will at least earn them a ticket, but in the US, it's just ordinary to spread out & 'drive' in an oblivious state...