I think that it would be a real stretch for any lawyer to sucsessfuly sue a poster from here for a snippit of code that someone else used in a program/script.
A lot of times it's just psudo code anyway. Here in Canada the junk lawsuits aren't as bad (yet) as they are in the US.
Having said that, a disclaimer on the site couldn't hurt. I doubt it would help though, there are to many cases where disclaimers/contracts were taken to court anyway.

I have written a lot of software for a lot of different people/companies and I have met a few that I said "no thanks" to and let the next programmer get sued.
In a nutshell, if someone really wants to sue you there isn't a damn thing that you can do about it. With a lawsiut even if you win you loose.