Imgur started off as a benevolent gift to Reddit users, but then as more and more people started to use it, the expenses became too great to keep it the way it was. There is no money in serving images directly with no advertising, but there is certainly costs. What were they supposed to do?
This is cyclical, an image site gains critical mass, builds in size and then buckles under the weight of providing a free, clean, high-bandwidth service.
