I'm astonished (was going to say surprised until I remembered the apochyphal story about Noah Webster) that no one has surmised that many of the their/there, its/it's, etc. errors may simply be typos which are not picked up by SpellCheck or whatever accursed automatic proofreader one's software uses, since they don't cite as an error something which is a real word, albeit not the one intended in the context. May the inventor and the distributors of these programs fry in the bottommost linguistic hell. Even good magazines and newspapers are coming up with errors because of homonyms which escaped the automatic spell checker.

Regarding who should have responsibility for the lack of knowledge of grammar and spelling, it's ludicrous to say that you need a lot of time. When I was in high school (mid-50's) there was a list of the 100 most frequently misspelled words in English. Every Monday and Wednesday, a list of 10 of these was handed out and every Wednesday and Friday there was a quiz on the list last assigned. The marks on this quiz figured prominently in your English mark for the quarter, semester and year. When you got thru all 100, you started over again. And this went on for 4 years. I may occasionally misspel a word, not thru a typo, usually a word ending in -able vs. -ible, but never one of the old 'top 100'. And the best part was that going over the list and doing the quizzes only took 10 minutes twice a week.