Where’s my ROI for Web 2.0????

During a recent conversation with a mate regarding Enterprise / Web 2.0, the dreaded question of ROI came back haunting us. While being a proponent on the benefits of Enterprise 2.0 is very simple, substantiating the need for Enterprise 2.0 in terms of $$ and cents may seem difficult, for now. 
ROI/Rate of Return (for some) [...]