This is huge from an academic standpoint, and I sincerely hope this sort of mind-expanding recommendation will enter the mainstream. Here is a off-the-top-of-my-head list of some introductory thoughts:

- I'd be willing to bet that people won't react well to this sort of thing popping up in their existing news feeds without their explicit permission. For instance, I'd love to see Facebook or Twitter introduce this as a ranking signal, but I can't see that resulting in meaningful discussion without some careful tuning.

- This being hacker news, the first thing that comes to mind is "let's found a startup that does this." I'd seriously love to see this turn into a product of some sort. It would face something of an uphill struggle for adoption, but it might not be so bad. One major feature of the "ideal customer" is already lined out: interest in or willingness to tolerate dissenting opinions. Synthesis of opposing views into a new one correlates strongly with education, so that's a group you can reasonably target. College students are into this sort of stuff, so you could go after them. Personally, I think this has potential as a space.

- Gathering existing data for this sort of thing could be difficult. Access to significant amount of social network data is a must, especially if you will want to perform clustering-type analysis. My hunch is that there may be a way to make this happen without a large quantity of data, but nothing obvious or market-tested comes to mind.