CopyrightTalk
It is very important that everyone working on Wikipedia respect copyrights. Since this is a wide-open project with no editorial oversight, this sort of thing will certainly happen again.
In our role as a provider of internet services, we have a fairly strong defense under the DigitalMilleniumCopyrightAct, and a fairly strong responsibility. We can't be held financially liable for other people's actions, so long as we follow a reasonable take-down policy.
Nonetheless, I can tell you that my charitable instincts and love of knowledge will hit the wall if someone sues me. :-(
Notice that I have added some more words at the bottom of the page. I think that the problem will mostly go away with this.
There is no way to be 100% safe. But, hey, risk is a part of life. --JimboWales