First, Apple made the highly unusual move of confirming that it would unveil a new offering, iCloud, at the Worldwide Developers Conference (WWDC 2011). Now, the company appears to have let slip the logo, as well.
Several pictures taken outside of Moscone West, where WWDC will be held, capture banners bearing the word "iCloud" together with an icon.
Apple Insider notes, "Inside, a huge banner depicts Mac OS X Lion, iOS 5, and iCloud as being the three components adding up for WWDC 2011. Additional banners hung from the ceiling are still under wraps. In previous years, Apple has kept some of these banners under wraps until the Keynote presentation."
The logo appears to borrow elements from both iDisk and iSync, as 9to5 Mac points out.
See iDisk and iSync logos below: