Phew, glad to know it's not just me!
I think I know what's going on.....
Some of you may recall that Imgur recently added video hosting to their service (within the past 2 weeks). I'm betting the video hosting is causing a major load on their servers, to the point where Imgur is running over capacity.
Embedding images may have been disabled by Imgur in an effort to 'throttle' the load on their system (to keep the whole system from crashing)
This is purely conjecture, as I have not seen any formal statements from Imgur. I'm simply going off my experience in the IT industry (data storage specifically), and the fact that they recently added a high-bandwidth service to their system