At Rypple, which furnishes Web-based team feedback software, the company uses Rackspace instead of App Engine because Racksapce made it easier to address concerns about security and privacy, said Tihomir Bajic, Rypple software developer. Customers, however, were more concerned about privacy of data, he said.

Simperium's Simplenote application, meanwhile, provides a way to keep notes on the Web, a mobile device or a computer.

"Simplenote actually started as a mobile app. We built it for iPhones originally and it's been around for over a year now," said Fred Cheng, Simperium founder.

in InfoWorld's Cloud Computing Channel.