This has been known for a while now, but achievements and trophies are no longer being actively tracked due to API headaches that caused the feature to constantly break. It might come back, but not for the foreseeable future.
Achievement support on the site has been (temporarily?) discontinued. The guys (Jeff and Dave) have talked about it in the past at length. The basic reasoning is that the API for achievements from those places is always changing and its a huge pain to recollect that information if it changes in any significant way. This link shows Dave saying that they aren't planning on working on it any time soon, but maybe in a couple months they will revisit it.
Here's a response from jeff's tumblr that talks briefly about why they aren't doing achievements at the mome
"Everyone wants achievements, too, but that’s a much stickier situation. We’ll probably wait until the new consoles launch and see if anything related to achievements/trophies change and then consider our options. Building site scrapers and all that other junk only to have them break whenever anyone makes a change (or blocks your IP because you’re scraping their achievement/trophy data) was a colossal pain. I feel bad for anyone trying to build an entire business around that data."
I'm pretty bummed about it, too. But I understand their reasoning.
I know it's boring to hear it over and over again, but hey, it's so easy to go "we've made the call so we don't want to hear about it ever again" and then never get around to it. So yeah, with respect, a nudge every now and then is in order :)