Kiddies cannot keep their hands off their . and / keys, though. They just go around ./'ing everything they can find vulnerable (which is very limited to them). Needless to say, if only real hackers know about it, then it isn't as big of a problem as it is with the kiddies. You don't have hundreds and thousands of little 14 year olds running around with codes that could potentially bring whole networks down when you don't disclose it, do you? There's a difference between fully disclosing shit (showing it to everyone on the net, which includes kiddies), and privately posting it to the vendor itself. Pr0j3kt M4yh3m for life. Props to Phrack High Council, h0no, dk, and other pr0j3kt m4yh3m cells for taking out the "big tough guys" in the whitehat security industry. It is a very big problem -- that is, the 'security industry'.
As I said, if a vulnerability is disclosed, then people have the opportunity to defend themselves against it. I'd prefer having the chance to defend myself than to have the chance of a 0day I never knew about hitting me. And to the people who don't keep up with the lists/updates, too bad for them.
But then you have script kids who can do all these lame DoS attacks and try to 0wn your box. Wouldn't you prefer posting directly to the vendor in a private manner so that kiddies can't get their hands on it? Seems like a better idea to me...
That way you're still getting your patches from the vendor... and, surprise... no kiddies can 0wn you! You still, no matter what, have little protection against the big boys though.
Let's say there's a vulnerability in Apache 1.3.33 that some researcher discovered. He decides to be responsible, and report it just to Apache.
Now, what if some blackhats already knew about it. They could use it to own my box and ruin my life, or whatever. I would have preferred him to post it publicly, so I could defend myself, than post it privately, which left me wide open and naked.
The sooner I know about something, the better.
Of course, there are other mitigating factors. For example, all I have on that computer is Apache/MySQL, and it doesn't have access to any other computers on my network. And the databases on it is backed up nightly. So the most that could be done is a defacement and an annoyance. But there is still a greater risk to me if vulnerabilities go undisclosed than if they are disclosed to all.