ROI for Web 2.0

1. Reduce cost of sale? faster sales cycle; increase yield
2. Reduce cost of lead generation? Less expensive marketing mix...
3. Reduce marketing collateral development costs and time?
4. Get answers faster
5. Reduce reinventions ... use the combo of bookmarks and search
6. Reduce errors
7. Speed up discovery process
8. improved quality of role-role interaction
9. Make faster decisions
10. transparent policy making lead to improved efficiencies
11. cost savings from shutting down low yielding projects

I would add several others:

increased win rate.
increasing customer retention
increasing number of non-competitive sales opportunities
increasing reuse of solutions
increasing utilization of subject matter specialists
greater job satisfaction
increasing customer satisfaction
increasing number of new service offerings
faster time to market