Leosghost - 9:10 pm on Sep 7, 2012 (gmt 0)
Why not? What stops him/her?
Probably the cost of copyright lawyers in the USA ( where most of the copyright and IP abusers, both the crowd sourced sites, and their members live, or in the case of the sites, are incorporated ) ..copyright lawyers do not tend to work on a "no win, no fee" or "pro bono" basis..
The sites are set up on the basis of them being able top "out lawyer" any likely complainant..into giving up before they start..or being prepared to spend vast amounts of money and many months if not years in court whilst the pinterest ( and similar site's lawyers ) stonewall and drag it out..
They definitely would not want to have a definite ruling by a judge or a jury against their scummy model , the jurisprudence would make a hole in the investments of their VC backers..