You might be interested in a similar situation that just played out in a California federal court.  Here is an over-simplified summary:

An adult entertainment company ("Perfect 10") filed a lawsuit against Rapidshare, alleging among other things that Rapidshare assisted people in infringing its copyrighted works by hosting copyrighted images on its servers.  Perfect 10 tried to get a preliminary injunction -- an order to get Rapidshare to stop the infringement while the case was pending.

Unfortunately, Perfect 10 lost this part of the case.  That does not mean they lost the lawsuit and preliminary injunctions are difficult to obtain.  It appears to me that the parties just settled but that's purely a guess, from reading between the lines of recent activities in the case.

Of note to vendors and Renderosity are these observations by the judge, contained in her order denying the preliminary injunction:

"... the [Rapidshare] Abuse Department was able to find and take down certain files whose download links were identified on the screen shots that Zada attached to his declaration . . . and also proactively searched the third-party websites identified in his declaration, such as filestube.com, and took down any files listed on those sites that appeared to be suspect. In addition, the download links identified in the complaint have also been disabled and the files deleted. The Abuse Department has also begun probatively searching Google and Bing.com for files that may contain the words “RapidShare” and either “Perfect 10” or the names of specific models identified by Zada."* (internal cites omitted)

Some issues with Rapidshare as to Renderosity items:  Can Rapidshare show that it has taken the same efforts to prevent infringement of Renderosity items?  Has Rapidshare searched the third-party websites such as TopGFX or the other warez sites like nigmae?  Has Rapidshare searched Google and Bing.com for files that may contain the words "RapidShare" and either "Renderosity" or models being infringed?

I bet the answer is NO!  That is how these third-party websites can continue to repeatedly make the same infringing posts as fast as Renderosity gets them taken down.

Instead of trying to go after the third-party websites which may based offshore, go after Rapidshare instead!  And Depositfile, and Hotfile, etc. etc.

Disclaimer:  I am a lawyer, but I am not your lawyer.

[edited by mod]