I have no inside knowledge (other than being in publishing generally) but they're in a hot space with relatively good advertising opportunities right now, they also run events which should, in theory, be quite profitable.

My totally unfounded theory/opinion is they were overfunded and the investors wanted to get out after not seeing the growth levels they wanted (which in publishing is not a big surprise, you almost never see SaaS or consumer app levels of growth there).

"It has run out of money"

https://twitter.com/mathewi/status/575090046572736512

LinkedIn blogs and news feed? That would be my guess.