For the first time since I joined the site, I just read the terms & conditions (link in the lower right hand corner of your screen). Here's the applicable section: :(
8. SUBMITTING MATERIALS AND FEEDBACK
Unless you enter into a separate written agreement with the Company, the Company does not claim ownership in Materials you submit, however, by submitting Materials in any form to the Company, in addition to other provisions of the Terms, you automatically grant Company a royalty-free, world-wide, non-exclusive, and assignable right and license to use, copy, reproduce, modify, adapt, publish, edit, translate, create derivative works from, transmit, distribute, publicly display and publicly perform such Materials for the purpose of displaying and promoting the Materials on any website operated by, and in any related marketing materials produced by, the Company and its affiliates. You obtain no rights in any form, media, or technology incorporating the Materials.