These incidents quickly gained attention in the Guild Wars community because of the very similar methods used and rapid succession of the incidents. Before long ArenaNet staff had stepped in to assure players they were aware, concerned, and working on it, and were able to release a bit of information. Support Liaison Gaile Gray revealed that "one of the trading sites associated with Guild Wars may have experienced a security breach and its account database (including user names and passwords) may be in the hands of hackers." The statement predictably invited extensive speculation, but at least told players that ArenaNet was making progress in their search.
For the time being, ArenaNet continues to work on the problem and players continue to get their accounts looted. (As of this writing the most recent reported incident was Sunday.) The issue continues to be widespread, with one alliance reporting at least eleven members hacked. It probably goes without saying, but while ANet sorts things out players can lower their risk a bit by changing their passwords and taking another look at the account security suggestions, if they haven't already.
Best of luck to ArenaNet in solving the problem soon!