man screws around with nature; natures screws back

I saw this story today. (there are any number of companion stories on Google news)
http://www.bbc.co.uk/news/science-environment-20025807

and I was reminded of the Eastern Ohio earthquake stories and their link to deep underground injection wells. http://pipeline.post-gazette.com/ne...d-deep-disposal-well-for-marcellus-wastewater (Again,you can find any number of articles about the link between injection wells (and by extension "fracking") and earthquakes. I chose an industry-friendly source for this citation.)

Obviously, a few rattled windown in Youngstown is not comparable to people killed in Spain, but the unanticipated consequences from unappreciated risks are similar. Predictably the extraction industry and environmentalists are at loggerheads over the risk. Industry soft-peddles the risk with a "Trust us, we're professionals" message, while the more wary environmentalists want no exploitation until all the risks are appreciated and back-up plans for every back-up plan are in place.

The Marcellus and Utica Shales offer promise of a large domestic natural gas source. Such a resource has very obvious economic benefits. Ohio's Republican administration and legislature went all in for "Drill baby, Drill" but the ODNR report suggests their enthusiasm was premature.

While the oil extraction industry actually began near here (Titusville, PA) NE Ohio and we've had gas wells here and there for decades, this area is generally inexperienced with large-scale drilling. So I'd like to ask (especially from those of you in the oil patch) What kind of risk are you comfortable with when the unintended consequences could include more serious earthquakes than the 4.0 in Ohio a few months ago? What amount of unknown risks -- the Rumsfeldian "unknown unknowns" are you comfortable with? Do you trust industry generally when they say there's no risk and they know what they're doing?