One of my first real jobs I had one of my responsibilities included reviewing technical support calls. It's hard when you hear people making the same verbal (or/or technical) mistakes OVER AND OVER.
I didn't mind correcting people's troubleshooting/technical mistakes (or asking them why they did it that way... maybe they were onto something I wasn't), but correcting language usage is always a tough one because it's REALLY hard to do it without sounding like a pedantic jerk, you have to concentrate on WHY it needs corrected (it confuses the other person etc) and not just because it's incorrect.
I just fly straight past pedantic and bring the full-blown asshole right away.
"There is at least as much need to curb the cruel greed and arrogance of part of the world of capital, to curb the cruel greed and violence of part of the world of labor, as to check a cruel and unhealthy militarism in international relationships." -Theodore Roosevelt