Microsoft's adding a new "social" search feature to Bing today that shows trending topics on Facebook and Twitter.

The beta feature was demonstrated by Senior Vice President Yusuf Mehdi at the SMX Advanced search conference this morning. It's supposed to appear on Bing later today (here's the Bing announcement and link to bing.com/social).

It's the first time the full "firehose" of Facebook updates has been incorporated into a search engine. Bing did the same thing with Twitter last October and is now blending both networks' update streams into its social feature. The sources appear in the left column of the page, which appears designed to add additional sources in the future.

UPDATE: The social feature still isn't live late this afternoon but a Bing manager said it's coming shortly. He said it's happening in concert with back-end upgrades.

Mehdi said Microsoft plans to continue its massive investment in Bing's technology and marketing to lure new users to the company's search service. Although it still trails Google by a mile, Mehdi said Bing's showing progress and getting new users.

"We've grown every month since we launched. That's truest proof case of whether its working or not," he said.

"Knock on wood, long ways to go, it's working."

To demonstrate how far Bing has to go, Mehdi showed a handwritten page of market research done by his elementary school-aged daughter, showing only four Bing users and a long list of her friends using the competition.

"She goes, 'Daddy, we have a lot of work to do.'".

Host Danny Sullivan pressed Mehdi for details on Microsoft's deal with Apple that put Bing onto the new iPhone. Mehdi said the discussion started when Microsoft developed a Bing iPhone app and was helped by Bing's visual interface that works well on the touch interface.

"They said our customers said they'd love to Bing and choice is good for consumers," Mehdi said, adding that "It was a very easy discussion."

Sullivan pressed Mehdi on whether Microsoft paid for Bing's placement on Apple's phone but Mehdi declined to say or provide details on the business arrangement.

Talking about Bing's office tower in Bellevue, Mehdi said they're interested in putting Bing's logo on the side of the building but "there's some issues with the city or the policy."

Mehdi hopes to revisit the sign issue but in the meantime an employee figured out how to have the building's interior lights spell out "Bing" at night.

"We find ways to overcome," he said.

It ended with Sullivan presenting Mehdi with a cake to celebrate Bing's one year birthday and the audience of search marketing experts singing "Happy Birthday."

"I don't think we deserve cake and candles - we have a lot of work to do definitely ... but it's been a great year," Mehdi said, thanking the industry for its support.