Not if you know what you're doing. Rearden Metal has made some great calls before earnings. I'm sure that he made the calls based on sound analyses of fundamental and technical data. http://www.elitetrader.com/vb/showthread.php?s=&threadid=73601&perpage=6&pagenumber=1
I have a lot of respect for RM and even accompany him during his current ADT short, but no one can consistently predict earnings reactions, there is so much volatility the amount of money that could be made using leverage and options is virtually unlimited, and anyone that could would be at the top of Forbes list for sure. It cannot be done, and never seen anyone that has done it.