Inkednation died because it was full of nitwits, assholes, hacks, scratchers, and nazis and it's content started to diminish in quality at about the same time that the owners decided to charge to be a member. It became harder and harder to weed through the muck and bullshit to find the good stuff and take it seriously. Charging for membership in and of itself isnt necessarily a bad thing, but they could never settle on a concrete plan on what to charge for or who to charge, and they implemented changes too abruptly without informing the members first, members whose content fueled the site to begin with. It had a lot of good qualities and members, and there were some stunning pieces of artwork on there at times and a lot of good information and debate going on, but in the end it fell victim to what seemed like greed, ego tripping, and general all around bafoonery.
A few bad apples really started to drive people away.