Getting your credit card company to do a chargeback usually will get you denied service from the retailer you did business with in the future btw... Nobody likes chargebacks. It's at the retailer's discretion, so just a heads up.
I e-mailed Mark yesterday with a question and haven't heard back yet either, though he does usually respond quickly. There could be any number of reasons he's not answering yet. I know sending e-mails every day is not the best way to get his attention. Just wait a few days between e-mails because he could have a backlog of messages to sort through. Also, check your junk mail to make sure you didn't miss anything.