In the arena of English errors, the GIGO process is perpetrated by spelling checkers. More accurately, it's perpetrated by the users of spelling checkers, who apply them to source material beyond the program's ability to help. The results vary according to the quality of the spell checking program. Remember, a spelling checker only works if the source word it is given is already close to the intended word. Nor will they find errors related to specialized words not included in their lexicon.
Spelling checkers are wonderful tools.
Just remember that as a hammer may mash your thumb, a spell checker may mash your words. The only certain way to be correct is to know what you're saying.