This is a tough question and one I've explored. Communities like 500px, gurushots, viewbug and a few others all have one thing in common. They hope that you'll buy into their services in order to gain a better shot at getting your images out there. All of these sites have a few other common traits which include having "ringers" at their site just so you or the average photographer doesn't win these challenges, its sort of a bate and switch thing. making you think you're winning then at the last moment pull the plug. This makes one think, Maybe i should pay for the new challenge and so on, never really winning anything but "points" though 500px and viewbug do offer gear for winning challenges. if I'm going to pay for something, I don't want anything to do with a virtual gallery cause anyone with my link can see my images as no online gallery is completely unnecessary. I think it might be good to try once or twice, which I did , but not anymore.