Destiny is currently experiencing issues with matchmaking and login on all platforms, according to a (since-deleted) tweet from the Bungie Help Twitter account. You can see a screenshot version of said tweet after the break.
This marks the first time since we wrote our week one State of Service review for Destiny that servers have encountered a serious problem. We have reached out to Bungie and Activision, and will update if we hear anything back.
Update: The only thing Bungie's Guardians should have to fear at the moment are the various agents of The Darkness out to blast them to bits; the servers are back up.