Depends on the media. Here is my scale of "lack of import to important" of grammar by written media type:
Text Message
Web Forum Post
Email
Briefing
Report
White Paper
Peer-Reviewed Document
WRT audio or video, I am likely to let grammar slips slide, due to the "thinking on one's feet" circumstance.
I don't get too bent out of shape by web posts that do violence to grammar, as long as they are intelligible. Some are, however, barely more than troglodytic keyboard poundings painful to decipher.
FTR, I do not spell or grammar check my web posts. What gets written gets written and that is the end of that, IMO.