Google has long used automatic image scanning to fight online child exploitation, but it's now clear that this monitoring applies to email, too. Houston police have arrested a registered sex offender after Google tipped them off to illegal photos of children in his Gmail account. The notice only led to a warrant at first, but it helped the cops discover locally stored images that they wouldn't have found otherwise.The bust is notable in that there were no public clues to the offender's activity, such as a website; besides the people he contacted, only Google would have known what he was doing online. That will undoubtedly raise concerns for some, since it wasn't immediately apparent that Mountain View's servers were checking Gmail images. However, the activity isn't a complete surprise. Google's terms of service already indicate that the company is analyzing Gmail for both targeted ads and security -- while illegal pornography isn't explicitly mentioned in the terms, it only makes sense that this content would be considered as well.