As a professional writer for 25 years, I can tell you that the new bread of "publishers" don't know how to proofread. They rely on spell checkers and grammar checkers, and the whole "Hey I'm human" mentality. You would not believe the number of times in a week that I write Disney to inform them of typos and horrid mistakes on their website. Now, I know that I am hard on the folks here on the DIS about writing, and heaven knows I've had a rant or two here, but the people who publish on the web are alleged professionals who should know better. Unfortunately, the attitude of "it's only the web, not a book" is far too prevalent.
That, I am afraid, is what it is coming to: It doesn't matter as long as I can get my point across.
P.S., I even find typos in the novels I read, and then have to go back and re-read a lot because I realize that I've been proofing not reading. Those are two distinct activities!