Location-based social network Foursquare has hired dashing French engineer Pierre Valade, creator of a very cool Foursquare/Twitter mashup called Agora, according to company statements on Twitter this morning. Agora sees who has checked in near you on Foursquare, then looks at everyone’s linked-to Twitter activity and recommends that you meet anyone who appears to have interests similar to your own.

That would be an awesome feature for Foursquare to add natively, though of course it can’t be presumed that something like that will happen. If it did, it would mean two things: that Foursquare had a whole new layer of social interaction added to it (which it could use, as an opt-in feature at least) and that a leading social network is in fact interested in pulling in publicly-available data from outside its silo and doing something really compelling with it. Who else does that? Not Facebook, not Twitter. The whole structured, public web of data outside those silos represents a huge loss of opportunity to add value for users. It would be great to see Foursquare buck that trend.

How many times have you checked in somewhere, seen that there are people in the same venue and had nothing but their mayorships to understand them by? If they’ve got a Twitter profile linked to their Foursquare accounts, you can click through and see their recent messages, but wouldn’t it be great if Foursquare did that automatically and highlighted anyone nearby that you might have a particular interest in? I think so.

There are of course as many possibilities for feature enrichment on such social networks as there are points of intersection between, and permutations of, publicly-available, structured fields of data.

The company may or may not engage in more of that, but the addition of Valade to the team is a cool turn of events given that he built this remarkable little app as a part of the first Foursquare Hackathon. TheNextWeb has good coverage of the app’s birth this Spring. Way to hack yourself into a cool job, Pierre.

Now let’s see what you can do as part of the team there.