When drilling in the Marcellus Shale began, videos such as this one made people fear hydraulic fracturing and natural gas drilling. People are able to light their tap water on fire because of the presence of methane in their water, and many people blame fracking for this methane.
While there have been some cases of well contamination, such as in Dimock, PA, fracking is not always the culprit. In some areas, methane can migrate into wells whether or not there is natural gas drilling nearby.
Most people never have their water tested for methane, so they cannot prove that natural gas drilling is responsible for the methane in their water. Currently, studies are being conducted to determine whether or not fracking increases the likelihood of methane migration.