Apologies for inadvertently contributing to the derailment of the original conversation. To me, like to most here, it almost seems comical when people write or speak poorly and then ask for business. It's not only a reflection of how they handle themselves, but how they will handle your business.
Of course no one is perfect, but there is a difference between at least some implication of an effort on the writer's part to put together coherent sentences, and complete disregard for punctuation and outright sloppiness. I don't know why, but perhaps with English being my second language, and having to try to learn it the best I can, I take particular notice and offense in this area as well.
Sadly though too many times in today's society, (prime example being our President), the amount of effort you put into this or other areas of education no longer seems to matter much when it comes to positions of authority. I comfort myself in the thoughts of one philosophy: In order for a person to achieve complete happiness and fulfillment in life he/she needs three things: power, respect, and sex. George lacks at least two of these, and the third, well I'd rather blind myself first...
Since people are mentioning books, the one I've found very useful and still reference is The Scribner Handbook for Writers by Robert DiYanni and Pat C. Hoy II.