Enterprise telecom expenses make up an average of 20 percent of your total IT expense line. Of that, up to 30 percent might go right into mobile services. Mobile is one of the strongest growth categories and offers immediate ROI in productivity gains, but uncontrolled expenses can explode your telecom expense. Some businesses pay as much as $2,000 per year, per employee. That's expensive enough when you only have a few mobile devices, but scale that up for thousands of employees, and you're looking at a massive number. MMS, EMM and MDM all promise to help control and cut mobile expenses, but what's the difference? Dig beneath the acronym to the actual services.