Mike Arrington from TechCrunch.com has written an excellent post in which he lists 10 types of Web 2.0 products the world needs, but which nobody has developed yet. Here’s his list :

• 1. Better and Cheaper Online File Storage
• 2. Blog/website Email Lists
• 3. Portable Reputations
• 4. Tailored Local Offers (via RSS)
• 5. Facebook, in other countries
• 6. Free Music
• 7. Open Source Yellow Pages
• 8. Podcast Transcriptions
• 9. Decentralized Review Aggregation
• 10. Build Something Cool with SSE (Microsoft’s new RSS extensions)