Just my two bits on this:
Bob, you said this: "After all, the wiki staff didn't violate my copyrights, a user did. "
Thats actually the purpose of the DMCA safe harbor provision. It only applies if a user unaffiliated with the site posted the material. They are actually obliged to delete the offending material within a certain time frame or be liable for violation if they do not.
If they posted it themselves, they are boned.
Bob, you said this: "After all, the wiki staff didn't violate my copyrights, a user did. "
Thats actually the purpose of the DMCA safe harbor provision. It only applies if a user unaffiliated with the site posted the material. They are actually obliged to delete the offending material within a certain time frame or be liable for violation if they do not.
If they posted it themselves, they are boned.