Alt.NET Podcast just featured db4o in Episode 14 entitled "Object Databases".
Guests to the podcast are Rob Conery and James Avery.
Topics discussed in the show:

• Object Database
• Database Styles
  • Integration Database
  • Applicatioon Database
• Matisse
• DB4Objects
• Crazy Talk: Reducing ORM Friction
• Database YAGNI
• Adoption of Object Databases
• Object Query Language

Enjoy! =D