One of my favorite (and somewhat underrated) services from Google is their photo management sofatware Picasa. They bought this from IdeaLab in 2004, but unlike numerous other Big Co acquisitions, it's kept improving.  It has a very smooth PC photo management client that is good at handling large numbers of pictures (though navigation is sometimes a little random) and seamless synchronization with the web version - 10GB of Google storage available for $20/yr.  It also plugs into a bunch of partners' online photo services, which we've used to print out hard copies and create photo books.

They just released version 3.5 and it has come with some powerful additional features, most notably in the area of metadata management - ie improving the ability to add people's names, places and tags to the pictures you take. I think this will be a key battleground in the coming years as content creation is democratized and every device worth its salt can create and distribute content. As pictures get smarter and tagged with machine readable information of what is happening in the picture, which namespaces will they be using? Will this be a way that Google can unseat the defacto address book of the world, Facebook?

Taking a leaf out of Facebook's stunningly successful social tagging feature allowing people to name the subjects of their pics, Google goes one step further - it learns who your friends are and then automatically populates their names as suggestions. You train it first by linking some names to faces, then like a well trained hound it  churns through thousands of  pictures, suggesting matches which in most cases are uncannily accurate.

Sometimes it grabs rather indiscriminately - heaven help you if you have one of those class photographs in the background of a shot - it will pop up another few hundred faces for naming, while you scratch your head wondering where they came from. One of the best matches was correctly identifying the portrait sitting on the piano in the background of one shot as being of my wife's sister - the portrait was taken 25 years ago.

Face matching on the web doesn't seem to have learnt from the PC app, so there's some duplication, and I am told I have 10,500 faces to tag (this is not my current priority in life though).  The open question is what happens next to all this data. There's a vibrant social graph being populated everyday by users that links Google's massive distributed contacts lists with faces around the world. Unlike Facebook it doesn't send a message to everybody who you tag, as that would be truly scary. It's up to you whether or not your name tags are displayed on your public albums, and there is a "report this" option if you find a tag on someone else's album that you want changed.

This is a feature that will be successful because it provides immediate benefit to the user - it's great to be able to create collages of your favorite nephew with one-click for example. However, there is something akin to driving SUVs here - it's fun and relatively costless in the short term, but is likely to be creating problems for people down the line. I suspect it won't be long before the first subpoena is issued to Google to support or deny someone's story in court. So if your conscience is free, happy tagging!