Auroracoin reached the $1 Billion Market Cap (artificially inflated) for around three quarters of a day before its mega dump.
As you point out, it was artificially inflated. It took advantage of the way market cap is calculated, which multiplied value across all coins in existence, when it really should multiply value across all coins
mined. Exluding massive dev premines.
Well that's actually most coins in existence. It's either a premine for the developers or its' held by whales who took it all for next to nothing. Dark was instamined by several million. 8 wallets (wallets =/= persons, aka could be socks) took 400 million NxT according to Salaczs' blog (NxT developer).
We've seen what has happened to all the 'fair distribution' coins. The capitalization simply doesn't hold as you can't control 1000 - 3000+ wallets. Even Stellar is seeing that with their tens of thousands of wallets where people are dumping instantly just to get $10.