I actually agree with whereisshe - I can't help but have a little smile at the images conjured up when people say they are defiantly doing something really mundane.
'I defiantly locked the car' did you give a hard stare to anyone walking past, daring them to challenge you?
More seriously, while I do have questions about the apparent low level of adult literacy, including the rather shocking stat I read about complete illiteracy, and where we are going wrong I try to let forum posts wash over me. My SpaG is frequently poor here as I type my stream of consciousness. What bothers me is the professional documents I receive written in a similar style, even CVs which state gcse English results and have a little blurb about being good communicators and that they always present a professional image, I always wonder what would be deemed important enough to use those skills on if not your very first point of contact with a company you would like to hire you?
But as long as there isn't wall to wall text speak and an op won't get shirty if I query their meaning (having seen arguments when an op got defensive after repeatedly using and defending the use of an incorrect word that made the op into something else entirely as they clearly didn't know what it meant) I'm pretty much fine with it. There are loads affect/effect, discrete/discreet etc.
When my posts stop looking like I fling punctuation at the page when I'm finished, then I'll criticise!