Face.com even has . Upload a photo, and it will tell you the mood of the person in the picture. It will also identify the individual's gender and report other details. It's designed for developers, but anyone can try it. (To use it, just click on the "upload photo" link in the left nav bar and choose a picture from your computer. Or, click "Use URLs" and paste in the URL of a picture online. Then click the "Call Method" button, and hover your mouse pointer over the picture for analysis.)

has been offering good facial recognition tools on since last year. The company has not announced a tool for detecting emotion. But algorithm-based data-crunching of the type that emotion detection requires is 's core competency. The company is probably working on it.

Google theoretically has a lot more access than to people's faces in real-time because of its Hangouts video service.

The company already demonstrates the ability to recognize the basic location of people's faces in . A goofy feature called Google Effects lets users add cartoonish caricature glasses, hats, beards and other "enhancements" to their own faces while using Hangouts. The technology makes it clear that Google can recognize faces, understand their orientation and features, and do it in real time at scale.

Google+ doesn't have advertising. But if the company chose to, it could easily add "mood" as a "signal" for serving up contextual ads.