Now, I do understand 500px is trying to create a uni-platform experience for its users, but now that 500px isn't allowed to publish their app, I'm sure it's only a positive sign for other market places. More and more developers will start (slowly, but surely) to neglect Apple's Appstore by default due to the fear of the ridiculous approval process and the uncertainty that their development efforts for the iOS platform may go a waste, because they have seen the history of popular apps like 500px and others.
There is a very thin line of difference between being an elitist and being a d*ck. Apple is making it clear to everyone that they are the latter.