Structure 08 all-stars Greg Papadopoulos of Sun Microsystems and Werner Vogels of Amazon returned to the main stage today for a fireside chat about how far cloud computing has come in the last year.

A major progress marker since last June has been adoption of the cloud not just by scrappy, broke startups, but now major enterprises. Said Vogels, “I have not seen in the recent history of technology something that had such a disruptive influence on the applications that are being built and the future of technology.”

But enterprises aren’t just handing their legacy software systems over to the cloud, and they probably shouldn’t. “It’s generally really hard and expensive and unwise to be moving your legacy pieces over to something like this unless you can really demonstrate the advantage,” said Papadopoulos. Instead, larger companies are better able to start from the ground up on new products that leverage cloud infrastructure.

Papadopoulos in particular pitched the cloud as potentially more secure than dedicated infrastructure. “I trust you with my life, Werner, you know that,” he joked. But seriously, he said, since clouds are expressly devoted to doing what they do, they are likely to be run in a more secure way than they would by enterprises that have to worry over more diverse businesses. That cloud-from-the-ground-up strategy is also starting to apply to software built on top of the cloud by outside companies, such as Tibco’s new Silver bundle built on Amazon. And since Amazon or Sun doesn’t have an interest in your stored records, for instance, they may be safer there than under the control of someone like Bernie Madoff, Papadopoulos said.

Video of the chat is here: