Anyone can connect and play at any time. If people who have bought the game only play on average for 1 month (which is unlikely), there would be 450k active players. It's absurd for someone to say that there are only 100k active players. GW2 is in all likelihood selling more than that every month. Personally, about 40% of the people I know who bought the game at launch are still playing. One of the players recently started playing again. Of course all 3.5 million who bought the game are not still playing but to say that 100k people are playing is equally absurd.