Merging late, and using both lanes to their fullest actually improves overall congestion (per Washington state, Minnesota, and others.) Merging early can lead to differential speeds between lanes, which encourages lane changing, which causes a general slowdown for everyone.

Use those lanes and zipper at the end!

One big problem I witness often is people exiting the open lane just to zoom to the front and re-merge back into it. Now they've changed lanes twice!

It's the 'zipper at the end' that most people mess up. I call them 'button people'.

I think the problem is that you have two sets of people when it comes to this topic. Those that know that the best time to merge is at the end, evenly dividing traffic in a 1:1 ratio. And the other group, which thinks it's best to "merge" early.

So, half the people merge early, creating a vaccum in the soon to be merged lane. And then the other half, fills it, which promptly causes the first half to think that they're taking advantage.

Worse still, there are some "road sherrifs" (in big trucks) that not only merge early, but also try to block the other lane when they see people trying drive that lane and merge at the end. At least in my country it is quite common and police does not seem to handle this properly.

It doesn't matter when you merge, it matters how.