Salesforce likely wanted to minimize the number of variables while the Checkout service is in its developmental stages, he said. "From my perspective, it was not surprising. It seemed sensible."

Appirio, which has products that integrate Salesforce with Google Apps, also develops natively on Force.com.

Salesforce's platform lets the vendor "focus on solving customer problems, instead of on back office or infrastructure," Ryan Nichols, vice president of products and marketing, said. When the Checkout service goes live, it will enable Appirio to focus on its software, "instead of developing yet another shopping cart," he added.

Salesforce first announced its plans for an e-commerce engine in late 2006.

Francis didn't provide a detailed reason for the delay. "A lot of it has been listening to customers," he said.

Part of the thinking behind the Checkout service "is pressure from Wall Street, which is asking them, how can you monetize what you do with AppExchange," said China Martens, an analyst with the 451 Group.

Then again, Salesforce's recent success in winning large enterprise deals may have assuaged investors and bought the company more time to fine-tune the Checkout service, she said.