Last fall, Google said that it was going to begin preferring websites that use HTTPS, and if there was any doubt that HTTPS was important, even the US government has made it clear that its own websites need to have secure connections across the board.
It looks like social site reddit is the next one to jump on board with the forced HTTPS, and I'd say it's for good reason, given just how massive the site has become, and given the sensitive subjects that can be discussed there.
As the above shot shows, it's already been possible to enable HTTPS on the website, but with it off by default, it doesn't serve those who are unfamiliar with the protocol. With this forced move, reddit is in effect better protecting its users, and most of them will be oblivious to it. I think that in a couple of years, it will not be uncommon to see most websites run through secure protocols.