16.4 Skype offers Voice over Internet Protocol (VoIP) telephony services and PC to PC calling. The telephone service began as a free service. Describe the revenue and profit model for Skype specifically. Has its acquisition by eBay changed Skype’s revenue model?

16.5 Salesforce.com sells software as a service delivered online.

Corporations pay about $60 per month for each user

(www.salesforce.com). Describe its revenue model and profit model.