Fake check scam. SDC sends a check (from a well known company, fake though it may be) and expects you to cash it, keep X amount and send the rest to someone through Western Union. The bank will then bounce the check as it is a fake and you're out X amount
They will pester you via email as a means of frightening you into cashing the check. They threatened legal action for not placing the advertisements and "costing them" for the time lost. They also are completely inept at expressing themselves through the English language.