A major feature of the recently released Google+ is Circles, which allows you to “share relevant content with the right people, and follow content posted by people you find interesting.”

Most people seem to look at Circles as a privacy feature — and indeed Google’s official description gives the impression that Circles exist to manage privacy based on real-life social contexts. Of course, re-sharing can result in unintended consequences, and Google even offers a warning that:

Unless you disable reshares, anything you share (either publicly or with your circles) can be reshared beyond the original people you shared the content with. This could happen either through reshares or through mentions in comments.

Privacy is a big deal, especially for Google — and particularly in the context of rolling out a new social network. Still, I’m not persuaded that privacy is the only or even the primary concern motivating the concept of social circles.

Sharing content with someone is not just about giving that person permission to see it. Sharing content with someone asserts a claim on that person’s attention. While it may be a privilege for me to have access to your content, it may be even more of a privilege for you that I allocate my scarce attention to consume it.

What if we focus on routing content to the people who would find it most interesting? Such an approach works best if all of the shared content is public with respect to permissions — that is, people post it without any expectation of privacy. Twitter demonstrates that many people are comfortable with such a sharing model. Imagine if they could learn to trust a system that optimizes (or at least attempts to optimize) the allocation of everyone’s attention. This is not an easy problem by any means, nor is it one that is likely to be solved by algorithms alone. It will take a strong dose of HCIR to get it right. But, at least in my view, optimizing the allocation of human attention is the grand challenge that everyone working with information retrieval or social networks should be striving to address.

Privacy is important, and social networks should offer simple, robust privacy controls that users understand. We all have experienced the problem of filter failure. But sharing isn’t just about privacy. Our attention is our most precious cognitive asset, both as individuals and as a society, Moreover, our attention faces ever-increasing demands as our social lives evolve in an online world relatively free of physical constraints. Social network developers would do well to pay attention…to attention.