The site belongs to them. Anything you submit belongs to them. If you gave a friend an apple, who would the apple belong to? Could the friend edit it by eating it? Yep. Could the friend throw it away thereby deleting it? Yep. If you don't want them to own it, don't submit it.
Please see: http://forums.cnet.com/5208-10152_102-0.html?forumID=97&threadID=249217&messageID=2494839
Why does CNET need me not to have any rights to my own content? What's the gain?
("Please note: All submitted content becomes the sole property of CNET Networks, and may be used, edited or rejected at CNET Networks' sole discretion. You acknowledge that you, not CNET Networks, are responsible for the contents of your submission.")

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic