I'm a pretty serious professional writer, and I get mildly (only mildly) annoyed when I see complaints about misspellings on web entries, because it often seems to me that the complainer doesn't know what he's talking about. I'm pretty good at grammar and once was a copy editor for a newspaper. When I finish a book, which usually will run 350-400 manuscript pages, I print it out and sit down with it and comb over it for these kinds of errors. When I'm done, I make the corrections and then make another printout and send it to my daughter, who is also a good copy editor. She typically will find another 1,000 or so errors and recommended changes...about 2-3 per page.
Most good writers don't write primarily by eye -- they write by ear. You don't say a sentence looks good, you say it sounds good. Good writers are trying to make their text sound smooth in the ear and brain of the reader. Unconstipated, if you will. One of the common errors I find in my own writing is the confusion of "their," "they're" and "there," which are pronounced the same way. I've known the difference between these three words since second grade, but because I'm primarily writing by ear, I sometimes use the wrong one. So I do not find it at all strange that somebody would write "lead" for "led."
I also pay no attention to typos in web postings, because web postings are usually a hybrid of conversational and written English, are done quickly and idiomatically. Caring about something like that reminds me of the nuns who'd get all over your case if you said, "Uh..." when trying to formulate an oral reply to a question.
The only thing that really irritates me is the use of "loose" for "lose." Those are not only entirely different words, but are pronounced differently. To me, that's like saying "cow" when you meant "horse." But then I always have to wonder -- when somebody accuses somebody else of being a "looser," is that sarcasm? Or ignorance?