Social mobile services provider Frengo is making available a suite of applications that run on top of and across Facebook, MySpace, hi5, Orkut and Bebo.

Frengo CEO Mahi de Silva points to what happened when the industry rolled out interoperability for SMS years ago. In the early days, users could send text messages only to other people using the same wireless network, but that changed after interoperability was introduced. Now, users can send text messages to people using other networks, and SMS has grown dramatically.

“That’s the same optimism we have for interoperability in social networking,” he said.

By way of example, Flirtable is the most-used mobile application on Facebook, and it’s one of the first applications to interoperate among social networks. Besides Facebook, Flirtable is now available on MySpace, hi5, Orkut and Bebo. Flirtable users can interact with other users on those networks.

Another application called LOLz, a collaboration between Frengo and I Can Has Cheezburger? also is available on MySpace, Facebook, hi5 and will be on Orkut later this month, the company said. The application makes it easier to upload content, caption or re-caption images and share the quirky images with friends.

Standard text messaging rates apply, but a lot of people interested in these types of social networking apps have bucket minute plans so they’re not charged per message, he noted.

The development layer that Frengo provides is available to anyone — from large companies that have a Web-based service they want to take mobile to the college student writing a Facebook app who needs help going mobile, he said.