Cloud computing may offer a quick and inexpensive way to build an online business, but customer fears about security still must be allayed.

Representatives of three cloud-based application companies touted their efforts Friday afternoon during an event at Google offices in San Francisco. Two of the companies, WebFilings and Simperium, were using Google's App Engine cloud while the third, Rypple, leveraged Rackspace cloud services but used Google technologies like Google Web Toolkit.

"We have several Fortune 100 and Fortune 500 companies that are storing their financial information with us and on Google App Engine, " said Daniel Murray, managing director of WebFilings, which provides an application to assist companies with filling out US Securities and Exchange Commission reports. WebFilings just signed up a Fortune 30 company also, Murray said.

WebFilings, though, still has to sell the cloud concept itself, Murray acknowledged. But a lot of issues as far as security are starting to fall away, he said. Both WebFilings and Google implement layers of security, said Murray.

"You have to make you can educate your customers and help them understand how [cloud computing] can be secure and how it can be a benefit to them," Murray said.

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 Baji?, 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.