Microsoft CEO Steve Ballmer attacked Apple's new MacBook Air laptop during a jovial interview with Apple evangelist turned venture capitalist Guy Kawasaki.

The question-and-answer session, which took place at Microsoft's annual Mix conference for developers, featured Ballmer's somewhat corporate answers to questions about Yahoo, Google, social networking, Internet Explorer, mobile devices and the forthcoming departure of colleague Bill Gates.

But the highlight may have been the good-natured verbal sparring between Kawasaki and Ballmer over the MacBook Air, which Kawasaki had in an envelope on his lap.

"That thing is heavier than the Toshiba I carry," said Ballmer When Kawasaki remarked that it was more powerful than Ballmer's Toshiba, he shot back, "that thing is missing half the features of a PC. Where is your DVD drive? Let me look for that."

Ballmer eventually held the MacBook and then slid out of his chair and fell to his knees faking that it was too heavy to hold up. Kawasaki then remarked that DVDs were passé, to which Ballmer bellowed, "tell that to your kids on a long flight, pal."

Kawasaki, who now runs Garage Technology Ventures, laughed and told Ballmer, "I'm never going to invite you back to Mix."

In another light moment, an audience member asked Ballmer to show some love for web developers like he had done in the past for developers as part of the famous "Monkey Boy" dance video that made the rounds on the internet a few years back.

Ballmer, always the salesman, obliged, standing up and yelling "Web developers, Web developers, Web developers" to the delight of the crowd.

When Ballmer said Apple had punted on the opportunity to get into the services game, Kawasaki said, "Apple might say you punted on the OS."

Ballmer quickly added, "They'd be wrong. Everyday, statistically, they would be wrong. Last time I checked we had a very high market share."

"Especially in the EU," joked Kawasaki.

"No comment," Ballmer said with a smile.

But Kawasaki wasn't all biting barbs. He congratulated Ballmer on Microsoft's success with Xbox and with Exchange email synchronisation, saying he could not live without it on this mobile device. And Kawasaki saluted the company in general.

"For the past few years I have been working with Microsoft a lot and it is a different Microsoft," Kawasaki told Ballmer. "There is not the arrogance, the bullying aspect, these people are really smart, really hard working, they answer email faster than other companies, and I want to give you a little bit of praise."

"Thanks, that is very nice," said Ballmer.

In between the banter, Ballmer talked about aligning with Yahoo and competing with Google. He acknowledged Microsoft was the underdog in online search and advertising, but said the company must have a strong position in both markets.

"It may be my last breath at Microsoft, but we are going to be there working away building share," said Ballmer.

"We do believe what will happen is you will get a few big online ad platforms that serve as engines of customer information, advertiser information, advertising insertion and intelligences for many, many sites on the web," he said in explaining why the company took a US$240 million stake in Facebook.

Ballmer said Microsoft developed Silverlight, its browser plug-in to support rich applications, in part so developers would not have to choose between basic web applications or rich desktop programs. "In some sense we have forced people who develop applications, who design applications, who design user interfaces, to choose this fork in the road," he said.

Ballmer said that there will be a lot more to show on Internet Explorer 8 beyond developer features highlighted a day earlier. "You should expect to see a lot more browser innovation from us," he said.

Ballmer said he saw social networking as an important concept going forward and that Microsoft would develop the idea both for consumers, such as with Xbox Live, and for enterprise users. He said there is no question that social networking is not a fad.

Responding to a question from the audience, Ballmer said Microsoft would have to take a long look at PHP-based applications if its offer to acquire Yahoo goes through.

"For those of you with PHP skills, we are going to make Windows Server the best place to land PHP apps," he said.

On the personal side, Ballmer described his typical day as one of three scenarios: on the road meeting with customers, in the office hosting continual meetings, or behind closed doors thinking, reading and digging into things.

He said he only receives about 60-70 emails a day and that no one screens them.

Kawasaki found that hard to believe, but Ballmer said he answers all his own mail or farms it out to the people who should be answering it.

Ballmer said he is driven by three things: that he loves what he does, that he gets to work with energetic and talented people, and that he enjoys a challenge.

Note: Image of Steve Ballmer via The Consumerist.