All great stocks hit new highs over and over. Some people only buy stock when they reach or approach their 52 week high. This may retrace a bit but I think if the market holds up it will beat the market. The fact that it is doing this well in these economic times boads well for the future. I don't really see a solid reason to take the risk and short this right now, but I see plenty of upside potential over the next few quarters. Having said that, I probably wouldn't load up on margin right now for the reasons you state.