Within hours of obtaining identifications of the Boston marathon bombing suspects, police likely obtained search warrants and extensive digital records from mobile phone networks and social media and e-mail providers.

The fast-growing rise of such data sets—and rise of network analysis tools to make sense of them—could provide a boon in the investigation. It might reveal the existence of other evidence, further plots, or the identity of accomplices. But sorting the real from the junk will be a challenge.

“The general number of law enforcement requests of e-mail and social network data has gone up by a wide margin,” resulting in huge stored databases held by police agencies, says Hanni Fakhoury, a staff attorney at the Electronic Frontier Foundation in San Francisco.

In the case of Google, such requests are rising rapidly. In the last six months of 2012, for example, Google reported receiving about 8,400 requests for user data, up from about 6,300 in the last six months of 2011. The company reports these data here.