Well now. Everyone has seen it. You're on IRC, or reading USENET, or just reading your email, and there it is. A message from some loser who thinks they're hot shit, or thinks that they are kewl, or 3|_33T. Sure, some of these people are sysadmins, or server operators, but if you think that being in charge of thousands of dollars of hardware and software gives you any level of maturity, perhaps you'd better think again.
Then of course, there are the ignorant multitudes. But take heart, many of them saw Hackers and The Net, so they know the deal. Fuck with them and they'll make you die like the rest.
Here are a few cases I've run across. Sometimes it's me, sometimes it's someone else, but it's always amusing.