My biggest bitch is the incorrect use of adverbs. Apparently around 1985 English teachers decided children no longer needed to concern themselves with adverbs and avoided teaching proper use of them. People have also become lazy and don't seem to care anymore.
I can catch about 40-50 a day which are improperly used if I listen to local and national news and sports shows, not to mention every day conversations
Knowing when to use "quick" or "quickly", "poor" or "poorly", "sick" or "sickly" and "good" or "well" no longer seems to matter to 98% of Americans