IHS CERA is a consulting company that works with the natural gas industry.
In this report they have some counterpoints about estimated methane emissions from fracking operations.
See the report here:
http://www.ihs.com/images/MisMeasuringMethane082311.pdf
what I surmise from this is that while we need better estimates, some amount of methane is escaping, and depending on the timescale, may really impact the GHG warming potential of natural gas, and consequently the qualifications for natural gas as a low carbon source of energy.

And here is another take:
http://www.timesleader.com/news/Study__Marcellus_gas_cleaner_than_coal_08-28-2011.html
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