I don't know what it is, it really doesn't make sense to me but I see it more and more. Maybe I missed something and this is the new spelling, but again it doesn't make sense. People writing things like "He might of been" instead of "He might have".
"I should of been working" instead of "I should have been working".

At first I thought it was a typo, but unless it's some kind of wide spread typo virus, it can't be a simple typo. So...