Hacker News on 21 December 2007

• A Tour of Xerox PARC
• Ask 37signals: Numbers?
• A Visual, Intuitive Guide to Imaginary Numbers
• Is your website a leaky bucket? 4 scenarios for user retention
• Seth Godin on Iminlikewithyou: Learning from flirting
• Tesla Asks Investors For Another $40 Million To Start Its Engines.
• Traffic jam mystery solved by mathematicians
• The Data Wars - Should Web Companies allow Mashups?
• Mixx Democratizes Categories: Something Digg Should Have
• Is Pownce Going To The DeadPool?