I think you missed the point of why he brought that up. He's not disappointed. But he's able to distance himself from his own experiences and view them from the perspective of Facebook and Twitter.
Sure, but that perspective seems to be "F'em, regular mallrat people like advertising. I don't personally know anyone that tacky, but I'm sure they exist and are ripe for the picking. All that's needed is a total disregard for everyone's opinion." Ugh. It betrays a contempt for, well, the world, and it is quite ugly.
I don't see it as an concession that people like advertising, but as one that in order for online applications like Facebook to exist, they need revenue. He's pointing out how Facebook can get revenue.
He is pretty explicit an unapologetic in the comments.
"Robert Scoble Says: March 21st, 2009 at 7:05 pm
Leo: you are particularly clueless if you think what I just laid out for you is spam. Advertising is NOT spam. A LOT of people actually LIKE seeing advertising."
"Robert Scoble Says: March 21st, 2009 at 7:25 pm
Will: I disagree. I know a LOT of people who enjoy being marketed to. Here’s a hint: they love going to the mall."
I was a bit over the top in characterizing it (eg, he does admit to knowing people who want stuff shoved at them), but these are his own words. Later on he adds some sops like "Zuckerberg told me he'll add filtering", but it's totally an afterthought.
Scoble is quite seriously telling Facebook to create its own reality over the opinions of the entire world. The potential profits are beside the point, at least for me. He's advocating a sad and ugly attitude.
Whenever I meet someone who says that s\he "hates advertising", I count the advertisements that they're wearing and carrying. It's always a non-zero number.
People do like advertising that provides value to them. They dislike/hate advertising that doesn't.