The hack resulted in a temporary cessation of registration, account management, and payment services. The company says that while the game servers are still up and running, "the gAS services might be down for a while." gamigo also says that it encrypts passwords and that "no access to account names and other data is confirmed."
[Thanks for the tip, Tim!]
[Update: gamigo has now posted a letter to its website discussing the intrusion and recommending steps players should take to reset passwords and secure their accounts.]