UPDATE: I CAN CONNECT AGAIN, AS OF ROUGHLY 20:07 GMT
I'm a Sky Broadband user, and a few hours ago I lost the ability to connect to imgur, including i.stack.imgur.com. All attempts to connect to any URL on imgur.com time out.
As a result, most of the images in questions and answers on StackOverflow don't load for me right now, and nor do some people's avatars. Pretty much every page I visit on StackOverflow, I get a loading spinner under my cursor that lasts forever, which doesn't render the site unusable, but is really annoying.
I'm posting this so that others experiencing the same problem and coming to Meta know that it's not just them, to make devs and whomever it may concern aware of the situation, and to enable discussion and speculation about whether this blocking is likely to be permanent and whether it's likely to be implemented by other ISPs in the UK.