The Seinfeld/Gates ad is so laughably bad that people are already building indexes of the negative reactions, less than 24 hours after it launched.
I have my own take on it.
Gates is the most recognizable geek on the planet. For most non-techies, he is the archetype of geekhood.
What kind of name recognition does Steve Ballmer have? Outside of developers, developers, developers, and developers. Would a silver-haired manager ever use him for a cheesy business analogy in a meeting? Nope. Blank looks all around. Tiger Woods and Bill Gates make good metaphors. Steve Ballmer doesn't.
Ray Ozzie? Not a chance. Even most techies don't know who Ozzie is.
This commercial wasn't about churros, The Conquistador, or briefs riding up. It was all about one line.
It slipped by fast, but that was it. That was the line where email@example.com began the public torch-passing ceremony.
A couple more spots, and we'll see either Ballmer or Ozzie entering the plot. Then we get the handoff, where John Q. Public is now meant to understand, "OK, Bill Gates has retired, but he's passed his wireframe glasses and nervous tics on to this guy."
Seriously, it's torch-passing. Don't believe me? You will when you see Ballmer air-running past a giant BSOD in the final ad.