The 2e definition of CN is a legitimate behaviour-type. Whether or not players can accurately portray such a character is up to the DM (I as a DM restrict CN and CE on a general basis because most players cannot accurately play them... ie... they would have to be prepared to be killed for doing something stupid without whining). A crazy outer power, for example, are CN in the 2e sense. The dumbed-down 3e definition doesn't fit them. The Outer Power is infinitely powerful, and random in its determination. There's nothing that it particularly values or devalues... there is only whim. In some ways, it's a non-alignment but for the sake of completion it's in there.
The 3e definition is, sadly, a bad combination of NE and TN: the selfishness of NE combined with the basic "I can't care because I'm neutral" of TN.
Most players can't portray this because they ultimately value their character. I think it's funny when a CN character behaves in a NE fashion consistently in hard times. This is the mark of a bad roleplayer to me (and, subsequently, a dead character).
ciaran