In my not so humble opinion there's no excuse for leaving commented-out code in a release. During debugging you might want to comment-out areas of code to see what happens and that's fine. Then you might decide that you want to remove certain parts permanently but also that you should be able to restore the code if necessary. That's what version control is for. My rule of thumb is to NEVER check in anything which contains commented-out code, because that kind of stuff tends to build up over time.

As an example, on one fairly complex C++ project I worked on , two of the other coders not only commented away code but also had little conversations in the comments, like this...

...
for ( i = 0; i < max; i++ ) {
   doSomething();
   // I really think this part should be removed. /Stefan 
   doSomethingElse();
   // No, it shouldn't. /Björn
}
... and even further down...
   // This code is strange. I fear it.
[download]

These guys shared the same room. Wouldn't it've been better if they'd talked to each other directly? :)

Cheers,
-- moodster