Yes it's true, CiviMail can be run on shared hosting! This enables small-to-medium sized organizations to run full scale massmailings and effectively target constituents and donors.
I came across a great quote in the CiviCRM year end review:
Technology is not a sufficient condition for raising nonprofit effectiveness. It is a well documented fact that technology only impacts corporate productivity when combined with changes in business process. Technology and business process together are necessary and sufficient conditions for increasing nonprofit effectiveness.
David Geilhufe - CiviCRM
This is so true. The crux of the matter in my mind is usability and flexability. Those changes in business practice can only happen if the technology can be molded to fit with the way the organization works. And the technology will only be used effectively if the organization understands how to use it.