This is taken directly from Cuusoo's ToS page:
"In exchange for use of the Platform, and to the extent that your contributions through use of the Platform give rise to any intellectual property right interest, herunder copyright, you hereby assign all rights worldwide to the content generated by you to LEGO, meaning that LEGO can use your contributions in any way and for any purpose, including to reproduce, copy, adapt, modify, perform, display, publish, sell, broadcast, transmit, or otherwise communicate to the public by any means whether now known or unknown and distribute your contributions for the whole duration of protection granted to intellectual property rights by applicable laws and international conventions."
They are the equivalent of Facebook using your profile and pictures for whatever they want. While them outright taking entire projects is unlikely for many different reasons, you cannot deny that the wording makes anything you put on Cuusoo theirs. Yes, piece and theme designers are only a small part of the entire process, and that they probably have quite a few years worth of ideas built up on their own. But you cannot deny that Cuusoo is, ultimately, a free resource of new ideas for Lego and I guarantee they have at least one employee looking for anything new to add to future projects. I know I am looking at this pessimistically, but I have worked for companies that have done similar 're-purposing' of existing ideas. You would be amazed at how sneaky large companies can be. I am sure most parts and ideas have already been thought up by Lego designers, but there are thousands of new ideas posted throughout the year on Cuusoo. Chances are there will be at least 1 or 2 that have something completely new to bring to the table. I am not trying to say that Lego will take everything they see, but we are providing them with ideas, on a micro or macro scale.
Well I don't want to hijack the thread... so I am glad Reids Hardsuit won. I cannot wait to see what Lego does to the final version. Hopefully it will look better than the Delorian