Well, my spelling, puctuation and grammar is usually pretty reasonable but I am aways happy to learn if someone spots I am doing something wrong - as opposed to a typo.
I was never 'taught' grammar at school but have made an effort after being taken aside on teacher training, very nicely, and been told by a Headteacher that I needed to do something about it because it would stop me getting a job. It didn't matter how good a teacher I was, people would make a decision based on my application. He also said I was not geing a good role model for students. I had a degree but my writing was inaccurate.
At the time I was upset but he was right. I was actually just lazy about it and I sorted it out really quickly. Once I had, I noticed it in others. Now after 13 years teaching, I see it all the time in parents many of whom who send really badly written. notes and letters or forms or requests and ae uncomfortale about writing. They will say, quite cheerfully, ' Oh I am rubbish at Maths' without any embarrssment but I have never met one yet who is not embarrassed if their written English is poor. (Note this is a 99% white working class intake.)
It matters. If we don't make ourselves write accurately we get out of the habit and develop bad habits that are hard to break.
Anyone with a learning difficulty may find accuracy really difficult and I sympathise. I am not about humiliating anyone and agree that once it's been said, it doesn't need re-saying and there are instances where it isn't appropriate. However, like any kind of factual accuracy or any opinion you express on social networking, you expose yourself to challenge.
Moancollins If you put £50,000 for a costing of £80,000 in you would be an incompetent who hadn't made basic checks on their work, could potentially have caused huge problems for your work and probably deserved to be sacked.
I completely disagree, it could be nothing to do with incompetency, it could simply be a typo and yet you have just judged me as incompetent and deserving of the sack. Hoist with your own petard there, I think. 
That is my point! Mistakes are easily made, should be pointed out and rectified and there is no need for anyone to be judged or sacked. Interesting that you are judgemental about that but not about accuracy in words.