-- people who don't know the difference between to/too/two
-- people who don't know the difference between you're/your
-- people who don't know the difference between their/there/they're
-- people who abbreviate words that don't need abbreviating, like "are", "because", "you", "between" and "tomorrow"
-- people who spell words wrong that they have no business misspelling
-- people who can't capitalize words in their sentences properly, or use proper punctuation
I could keep going, but I'd take up a lot of bandwith. Let's face it, English as a written language in this country, especially on the internet, is no longer a priority.