People being hacked since the last Server Check.

How exactly would they do that?
Would some programmer deep in the bowels of Nexon HQ's spider sense start tingling?
Would some great alarm go off somewhere?
Would God Himself Manifest before the office to explain to them what happened?
Will Gandalf The Gray Stand before the hackers and shout THOU SHALL NOT PASS as they try to break in?

You of all people should know that a major company like Nexon has logs that monitor this kind of activity. You can't go around telling me that if someone was accesssing your SQL Database through unconventional means you wouldn't know about it.

A program only does what it's programmed to. Unless they specifically designed it to recognize that it was doing something it wasn't designed to, how exactly are they going to be aware that it's happening? The very fact that someone logging in this way is a bypass indicates it's something they didn't anticipate being possible, therefore how exactly would they have security measures in place to identify it was happening unless they went out of their way to add them in to try to identify them happening? Which would require them to admit it was possible in the first place.

Logs.

You have no more foundation for your "couldn't happen" than the other side does for their "could happen".

There are a finite number of ways to hook into the keyboard input and most decent antiviruses can detect any process that is doing so, short of it being rootkitted because they don't need to know to listen for specific programs, they look for specific behavior and any process behaving that way is suspect.

Would you like me to start releasing programs that look fine, and then release the list of accounts that were stolen from them?
Edit: Just as an addition, I'm using "keyloggers" as a very broad term here. There is more than one way to steal user input, it doesn't have to be just hooking the keyboard.

This too is bullpomegranate. Security is not entirely on the users side. Did the people with accounts as Sony download anything? No. Sony was breached. Assuming Nexon is immune to breach while larger more sophisticated companies are not is delusional. The vast majority of us who have been hacked did not download a keylogger, pure and simple. Blaming it on a trojan, a keylogger or the end user is a cop out. Yes the end user is occassionally responsible, and during normal 'hacking' almost exclusively responsible, but whatever has been going on with Nexon lately is clearly a flaw in their security for at least a substantial portion of the intrusions that are occurring.

You just said that if someone hacked a database there would be no way for the company to know about it. How then, did Sony shut down all of their servers while trying to remedy it? Stop contradicting yourself and using hackers as a scapegoat for end user stupidity. Monitor your damn forums and stop letting executables that have no proof of legitimacy run wild. Not so much as a virus scan has been posted for EITHER of them.

A keylogger would not explain accounts that have been untouched in years being opened despite strong passwords. A keylogger would not explain people who have common sense.

Just because they aren't playing Maplestory doesn't mean they're not visiting Maplestory related websites, or downloading programs. As for the common sense thing: People never admit to downloading keyloggers. Every person who's been hacked is a saint and has never touched any "bad websites" or malicious programs in their lives. The truth is that is a load of bullpomegranate and everyone knows it.