Diabetic Investor has long held the belief that the only way a company like Tandem could eat away at the huge share held by Medtronic was if Medtronic screwed up the goose that lays the golden eggs. Based on what we're seeing in the marketplace this is exactly what's happening. To make matters even worse for Medtronic it now appears that they are losing the battle keeping existing patients, which is patients whose pump is out of warranty. Rather than upgrade to another Medtronic pump these patients are now opting for either the t:slim or the OmniPod from Insulet (NASDAQ:PODD). This is not good news for Medtronic who makes a bundle from the continual sales of pump supplies to their once huge installed user base.