I would never fault a non-native English speaker for their errors. I write quite a bit in Spanish (usually emails and SMS) and I am pleased to not have people point out my errors (at least in a smart-ass way, but I do like to know when I've screwed up). Of course, in emails I use a spell checker in both English and Spanish...
But what does crack me up is when I hear Spanish-speaking people tell me how it's almost impossible to mess spelling up in Spanish. I reply (in letters, in my head) "noce, que vueno para vs..." hehe. And let's not even talk about accents in words and verb tenses that can completely change the meaning of what you're trying to say!
Truth is, in this day of spell checkers, we should all at least get the spelling of words right. I use Firefox which has built-in spell checking, when writing online. I very rarely don't know how to spell a word, hell I'm an avid reader and I've been writing for 45-some-odd years, but my fingers do slip up now and then.
But to me the worst is, from native English speakers, who confuse "there", "their" and "they're" consistently, along with other similar things like a "mute" point (thinking of "moot"). I saw someone use the word "indite" for "indict" the other day, don't know if the writer was native English speaker or not (don't even remember who it was).
Every now and then I find myself making some of those errors when I'm typing rapidly - but I go back and re-read what I'm writing. I guess too many years as a manager in a large company, and running my own small company, forced me to ensure that my communications, while they can at times be quite long, are at least mostly readable. Some would say that my ramblings are as bad as misspellings perhaps...