“PCs are like trucks,” Apple (AAPL) CEO Steve Jobs told Walt Mossberg Tuesday night at the Wall Street Journal‘s D8 conference. When America stopped being an agrarian society, people started buying cars. Devices like the iPhone and the iPad, in Jobs’ analogy, are the cars of computing as society transitions into what he calls the “post PC world.”

“And this transformation is going to make some people uneasy,” he predicted. “People from the PC world.”

Enter Steve Ballmer, CEO of Microsoft (MSFT), who was, in his D8 turn two days later, the embodiment of the uneasy PC guy, whether attacking Google’s (GOOG) “incoherent” operating system strategy, damning Research in Motion (RIMM) with faint praise, or dissing Apple as living in “the bubble of Terranea” — a reference to the swanky resort where the conference was held and whose participants could afford to own “five devices per person.”

All Things D has posted excerpts of Ballmer’s interview (along with Ray Ozzie, Microsoft’s chief software architect) on its D8 site. We’ve pasted several below the fold, along with the Steve Jobs video that includes his vision of the post-PC world. It begins at the 3:30 mark in the first clip. Ballmer’s response is in the video about the iPad.

Steve Jobs on the iPad and the post-PC world:

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Steve Ballmer on the iPad:

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Ballmer and Ozzie on cloud computing:

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Ballmer on the battle for control of the mobile phone business:

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See also:

• Videos: Steve Jobs talks about Flash, Google, Gizmodo, AT&T and more
• Microsoft in the Steve Ballmer era

[Follow Philip Elmer-DeWitt on Twitter @philiped]