The major ideas that Schroeder claims was stolen from him include content boards and infinite scrolling. Additionally, Rendezoo was said to have targeted females and Pinterest has a huge female membership which is said to be another sign that Pinterest used ideas belonging to others. The site has responded by saying that the lawsuit is "baseless" and will be "aggressively fought".
Pinterest is a site that allows members to "pin" pictures and images of things that are important to them and share it with the rest of the world.
source: AllThingsD via SlashGear