Google's new email is generous with hard disk space and generous with search capacity. Why are they being generous? Well, there are probably several reasons. The main one is that they get the power of information. They know that if you give people space and ease of access they will communicate and share. If you put controls on them they will automatically be more reserved. Look at hotmail.com or yahoo.com which put limits on their mail. They did it to control costs but they drove away the interaction of the people.
Generosity pays. The more people have rooom to interact with each other on their terms the more likely they are to be creative and generous.