Apple.com/business has published a case study of micro-blogging darling, Twitter. Not surprisingly, Apple.com gives Twitter a lot of love for loving Apple products, especially the iPhone:

When it comes to availability, iPhones accommodate peoples’ needs to work remotely and stay connected with the Twitter team. Stone notes that Twitter remains loyal to iPhones even though other handset manufacturers offer them free equipment.

Not surprising. The price of a thing is seldom equal to its cost. If a free product takes you more time or resources or requires greater infrastructure to support, the cost of using it can rapidly grow higher than the dollar price of even a premium product or service.

For businesses that thrive on the technology the iPhone best supports, web, media, and a certain strategic perception and mind set, paying for iPhones is probably a much greater value than any "free" phone.