@ Calabar
Yes, Lego did provide us with a great tool to express our creativity. Nevertheless, the world isn't black & white, and the good guys are not always the good guys. Let me quote the legal notice found on the Lego website, so that you know what we are talking about here. Lego says:
4. Any communication or material you transmit to the Site by electronic mail or otherwise, including any data, questions, comments, suggestions, or the like is, and will be treated as, non-confidential and non-proprietary. Anything you transmit or post may be used by LEGO A/S or its affiliates for any purpose, including but not limited to reproduction, disclosure, transmission, publication, broadcast, and posting. Furthermore, LEGO A/S is free to use any ideas, concepts, know-how, or techniques contained in any communication you send to the Site for any purpose whatsoever, including but not limited to developing, manufacturing, and marketing products using such information.
See what I mean? Anything you send to Lego can by used by Lego in whichever way Lego desires. Let's say a professional designer spends a few months designing an entire new theme world for Lego and that designer wants to suggest this to Lego, hoping to earn some money. So he sends some pictures to Lego by mail. According to the paragraph above Lego would then have the right to produce and sell the theme world without paying the designer a penny.
Of course I am aware of the origin of this paragraph. In large companies, these kind of regulations are thought up by the lawyers to protect the company. Because maybe Lego is working on exactly the same idea the designer above sent them. In such a case they want to avoid being sued by that designer. So Lego has a good reason for such a regulation.
Bottom line: The fact that Lego claims this right doesn't mean they would really act this way. So unless Lego actually does disrespect copyrights and does use uploaded models I don't want to accuse them of anything. But I don't want to take the risk either when uploading commercial work. So I will continue looking for an alternative solution.