The growth of Facebook has added a new element to flirting: now, on top of mix tapes and coffee dates, flirting now often includes trading links through Facebook posts. If you think two of your friends may be on the verge of joining up, says Carlos Diuk, a data scientist with Facebook, look at their Facebook exchanges. In the build-up phase to the formation of a new relationship (or, rather, the public declaration through a Facebook status change), Diuk says, the new couple will post more and more on each other's walls.
Once the romance is official, however, the interaction plunges. Diuk says this is because, one can assume, the new couple is probably hanging out rather than sitting around awkwardly flirting with each other on Facebook.
To be fair, though, this pattern is probably true for all sorts of relationships—not just the romantic sort. Sometimes sharing a cat video doesn't mean anything more than "Please look at this cat video." As with all types of flirting—longer-than-usual conversations, little touches, secret smiles—the intention of Facebook over-sharing can be ambiguous.
H/T The Atlantic