There is some trouble lurking here:
"The Electronic Communications Privacy Act (ECPA) [18 U.S.C. Sections 2510-2521, 2701-2710], which was signed into law in 1986, amended the Federal Wiretap Act to account for the increasing amount of communications and data transferred and stored on computer systems. The ECPA protects against the unlawful interceptions of any wire communications--whether it's telephone or cell phone conversations, voicemail, email, and other data sent over the wires. The ECPA also includes protections for messages that are stored--email messages that are archived on servers, for instance. Now, under the law, unauthorized access to computer messages, whether in transit or in storage, is a federal crime." http://www.pbs.org/wgbh/pages/...
It is not clear to me that Google has the legal right to look into email beyond the notion of
presenting marketing content that lines up with a user profile and perhaps a blind data
base match against market content and marketing profiles.
Since CP is illegal no profile or other marketing activity can be sold or participated with
by Google. To me nothing in any market driven activity can generate a CP profile
and match.... the implication is that someone was buying or selling Google services
to engage in CP.
It is possible that an image was discovered and a federal warrant caused Google to
search for a match against a very specific image. The sharing of such images outside
of law enforcement may itself be illegal especially if a service to discover such an image
if Google was paid to search for it.
It is possible that an image transfer to a different suspect or legal honey pot
was detected but that should trigger a search warrant.
As others have pointed out anything seen and disliked or disliked and searched
for but not illegal could trigger a witch hunt. I know individuals that have a
visceral dislike for: Rush Limbaugh, CNN, FoX, Kate Gosselin, Jodi Arias,
Joe Arpaio and some would have inclinations to make accusations if they
thought they could get away with it.
The good thing at this moment is that I do not know enough about this
in any detail so others will have to dig into the reality.