I don't know why billion coin is third most traded coin so far but I bet it has nothing to do with the chat feature...
Pump. No chat feature will bring a constant 1 mil $ trading /day.
Don't forget that 99% of the trading volume comes from BTC38, a chinese exchange. I don't know their trading fees, but many chinese exchanges have 0% fees. It could be a group of traders buying and selling into their own sell/buy walls to create the false impression of gigantic volume.
Many people know that volume precedes price, so they start buying into the coin, in the hope that the price will rise. This indeed will lead to a rise of the price, only then to get dumped on by the very people which initiated this huge volume. A good strategy by those guys, and quite a few people fall for this stuff.