There's definitely a line between "good snarky" (where the question gets answered or the poster gets pointed at the right solution) and "bad snarky" (where we're just being mean) -- I can't think of any SF regulars, myself included, who haven't occasionally stepped over the line into being mean, and I think it's something we all need to remain cognizant of when we answer "marginal" questions.
That said, sometimes I feel a little snark is called for -- not to be mean, but to remind certain folks asking questions that system administration is a specialist profession that is perhaps not for everyone, people who are substantially out of their depth and need to Seek Professional Help, or when dealing with folks who "just don't get it".
A couple of cases in point from my answer history:
How to transfer a domain name with 99.9999% uptime? - slightly snarky, probably preachy, but explains why they're looking in the wrong rabbit hole and aims them at a solution.
Am I getting DDoSed, and what should I about it? - 99% pure snark and I'll admit it - This was "HALP! I R BEING DDoS'D!" question number 1472 for the week and this poor guy got hit with the deadly snark-ray.
I deleted files from my Linux box's /boot directory and now it won't boot - Preaching from on high, with plenty of extra snarkbiscuits, but in the grandest tradition of system administration "Ok, you broke it - YOU get to fix it. Here's the instruction manual and a screwdriver".
Pretty much every DNS question I've ever answered - Which all begin or end with some variant of "If you do not currently own a copy of DNS and BIND you really need to go buy one and read list of chapters before continuing to mess about with DNS".
