I think a lot of bag companies wind up having similar type designs...probably based on design trends and stuff like that. I think that's just something most products deal with.
The only thing Marc Jacobs probably did in relation to that bag was put his X on a piece of paper approving the production. It's Marc by Marc Jacobs, his diffusion line, and I'm pretty sure that it's strictly a name-licensing deal, i.e. he he has a team of designers who handle all the real work of creating the clothes and accessories. Correct me if I'm wrong, though.
^^^ that "multipocket" bag is called the Sophia. this is where the Koala locks came from. the one the looks like the Manhattan is called the Venetia. im pretty sure this MJ bag came out at least a year before the LV version.
here's the Venetia: