Of course it causes earthquakes. We NEVER have earthquakes in the UK (ok not never ever, but they are rare as) but since they started a test drilling site for fracking in one area it suffered a number of small quakes. Nothing major but enough that it was obviously connected. http://www.bbc.co.uk/news/uk-england-lancashire-15550458 Gas Fracking Probably Caused Blackpool Earthquakes in U.K. - Businessweek
...keep in mind fracking per se is not the suspected cause of the earthquakes. Rather it is wastewater injection into the earth as a method of water disposal being used by a Ohio waste disposal company, and also some other states. Obviously it calls this waste disposal technique into question.
Is it obvious? For those of us living in active tectonic zones, isn't it better to have that constantly accumulating tectonic energy released in many innocuous microquakes instead of a few catastrophic megaquakes?