I was especially delighted by the discussion after Joshua introduces the upcoming "network" and "group" features, where groups are opt-in collaborations and networks more like the current inbox feature, in that users won't be told that you have included them in your network.

Excerpt:

I point out that flickr tells you. Joshua says that every time he gets a notice from some random person that he's been added as a contact "I want to rip my face off."

Joshua: "I'm not trying to build up the delicious community. There are plenty of communities."

That definitely resonates with me, and now I understand why inbox-subscriptions on del.icio.us are one-way streets. I've been planning to filter out comments from Flickr pages for months now, but haven't found a decent Greasemonkey-alternative for Safari yet. Well, wait and see, MouseHole is looking more and more interesting...

A bit further down:

Q: Are you building systems to monitor the trends of what people are doing?
A: Right now it's not hard to identify the outliers. It's not our focus. But my background is in analyzing bulk data.
Q: How about letting your users see that data?
A: I'm generally wary of this. If I publish the most clicked-on list, then it becomes a high score list that people will try to get on.

Other interesting bits:

• Only 10% of del.icio.us visitors are registered users!
• Amazon is one of the top bookmarked sites, but not many people tag with ISBNs.
• The number one bookmarked site is delicious itself (huh?)
• Almost no one subscribes to a person/tag. Most subscribe either to a person or a tag.
• Is Joshua/del.icio.us actually the originator of tags? The transcript makes it sound like that.
• del.icio.us is implemented with Mason, a Perl-framework for web development.

...and after using Rails for a while I can definitely see how more lightweight frameworks like Mason make sense for high-traffic applications.