Shares of Rackspace Hosting (RAX) gapped down nearly 18% in early trading Wednesday, after the company missed Q4 revenue estimates and got a downgrade from Stifel Nicolaus. As IBD reported, revenue growth from cloud computing decelerated, as the company continues to rely on its legacy Web-hosting business. In its earnings release late Tuesday, the provider of cloud infrastructure services didn't provide guidance, as usual, but Stifel analyst Todd