-- Lost a lot of trust in the userbase when they did the ridiculous "Matt has viewed the following questions" stunt.
-- Kicked one of the 2 co-founders, Cheever off, rumour has it he didn't want to go as aggressively after growth as D'Angelo & other powers wanted.
-- Widely sneered at in SV as being the company to look at if you want to know what "taking it too far with forcing growth" means. Their "sign-on to view this content" is a joke. Especially if you combine with their "Our mission is to grow and spread the world's knowledge"
Personally:
-- Their site's JS is a fucking mess. Crashes both my Chrome _as well as_ my iPhone's Safari frequently.