Their potential revenue is a huge concern. They don't even have a real revenue model. Literally the entire game is free. In LoL you still have to unlock champs, which are now always 6300 IP, so it gives good incentive to spend money, along with many high quality skins. What is there in PoE? Don't need extra character slots, the standard inventory/stash size is fine, and the character models are too realistically shaped for skins to significantly change their look like LoL and other mobas.
My prediction is the game will run off of this huge initial swath of support with the donors and kickstarter and then either one of three things happen, 1) it dies off, 2) they create an auction house, 3) major content will cost money (new acts).
Can't wait till the game goes live. Had a blast with the beta.