Whenever I look at job resumes (which I have to do from time to time), I usually immediately bin anything that is poorly written or poorly presented - and this includes poor spelling.

Of course. So have I, but to fail to discriminate between a formal document like a job application, and an informal communication like a posts on PM, Usenet or irc does no one good service.

... and another native English speaker who is just being plain lazy.

There are many reasons why a person, such as myself, may be prone to misspelling words. To blithely attribute them all to laziness, is itself a form of laziness. A failure to look (or care) more deeply.

Spell checkers can help, but they are far from infallible with the propensity of English to have so many homonyms. They also require time to use. Time well spent upon formal documents, though it is no substitute for proof reading by someone with the appropriate skills. For informal documents, it is time that must be taken from other, more important activities.

Some of the most capable programmers, including a few high level monks, produce excellent code but very poor documentation for it. Technical writing is a skill all its own, and the best technical writers are rarely programmers.

Your association of poor spelling with "sloppiness and laziness", probably says more about you, those those you diminish and reject on the basis of it.