People being hacked since the last Server Check.

Although It might not be efficient in terms of NX purchases, You can always just have a seperate account for each game you want to play.

Even this is not necessarily safe. There have been reports of people playing other Nexon games who have never played Maplestory still having NX stolen through Maplestory MTS purchases. The hackers either create a MS account to make the purchase, or have some other more clever method.