There's a book called I Judge You When You Use Poor Grammar. I haven't read it, but it's one of those books with fun English language gaffes and flubs. I've read several of these kinds of books and enjoy them. However, I can find enough of these kinds of errors without buying a book or even looking too hard.
Let me back up a second though and assure you that I personally don't judge people based on their grammatical goofs--that's just the name of that book. It certainly does make me sad, though, when educated people make obvious errors; and I think it says something about our country's education system. Communication is one of the most important skills to have in today's world.
It's understandable when people write un-grammatically in a text message, in an informal email, on Facebook, etc., but too many times this informality carries over into the professional world (which seems to be gradually getting smaller and smaller). Proofreading what you write before hitting "send" is an important step to consider. Last week I received an email from a buyer at the corporate office of the company I work for. I was the only recipient and I knew she had been writing it in a hurry, so the error had minimal consequences. She wrote that she "defiantly need[ed] a second pair of eyes." It was apparent that she meant she definitely needed a second pair of eyes. (And, she obviously proved her point!) No harm done.
However, this same company regularly sends out "professional" communications to upwards of 1000 recipients at a time. Not only are these riddled with vague directions and poor organization, they also often contain sentences that are just plain painful to read. For instance: "We are giving store management the opportunity to review the list of patrons who our systems show should be sent to collections before they are sent." Or, "...the PSC will be putting together a patch that will that will update all store's flash plug-in." No, I didn't accidentally write that will twice; that's how it was published. And "all store's flash plug-in"? Ugh. That should be "all stores' flash plug-ins." In these cases, yes, I DO judge the company I work for. I don't judge the actual individual who wrote the sentences though. Not everybody is a grammar guru; not everybody has to be. We all excel at different things. But, for crying out loud, there should be somebody looking over these communications before they are sent out for 1000+ people to read.
Think about the image you want to project when you write something, whether it is personal or professional. Although someone might not be "judging" you, per se, for writing it, he or she just might end up using it as an example in a blog or a book of English errors.