Commodity is when your product has no differentiation on the market. Imgur does not have enough differentiation on the market and that's why they're a commodity. For image centric community you can go to Reddit, Tumblr, or any kind of online forums really. Youtube's differentiation is that it has created significant network effect around public video hosting. Can you think of any meaningful competition other than Vimeo? (Or maybe a couple of others but they're nowhere as close as all the online forums online)