Check out this link for a great list of the top 10 grammar errors. Numbers 1, 2, 3, 4, and 5 all have to do with commas and seem to be right on target. You might also find it interesting to read all the way down to the bottom to find out how spelling can relate to recruitment. I know I did!
Source: www.grammarcheck.net
http://www.grammarcheck.net/oh-my-grammar/
Lisa Sturgis, UC VAWLTer