Many people chose to buy a theme, so that only their site can use it. Others make their own, and some people just use free themes. What is the best choice? I guess the best choice, is to buy a theme. But this is not that great of an option for people with a tight pocket. Making your own theme is not a good idea unless you are really good at it, because it is time consuming and the end-result probably wont look that good. Using a free theme poses the risk of sharing themes with several large sites, and that's detrimental to your own site. I don't think Google cares about duplicate themes though, just content. Where did you get your theme?