It does seem odd that Cramer's "The Street.com" has a SELL rating with grade D- in their report updated 3/20/11, when the price was at $13.30. Sounds like he's setting it up for his buddies to short.
excerpts: "This stock has increased by 38.11% over the past year, outperforming the rise in the S&P 500 Index during the same period. Regarding the future course of this stock, we feel that the risks involved in investing in DXCM do not compensate for any future upside potential, despite the fact that it has seen nice gains over the past 12 months."
"VALUATION: SELL. This stock’s P/E ratio is negative, making its value useless in the assessment of premium or discount valuation, only displaying that the company has negative earnings per share. For additional comparison, its price-to-book ratio of 13.54 indicates a significant premium versus the S&P 500 average of 2.18 and a significant premium versus the industry average of 4.06. The price-to-sales ratio is well above both the S&P 500 average and the industry average, indicating a premium. Upon assessment of these and other key valuation criteria, DEXCOM INC seems to be trading at a premium to investment alternatives within the industry."