web 2.0

Why are email services like Hotmail, Yahoo, Gmail, AOL etc. free?



Almost every email service today can hold GBs of data, the company does not cost even a penny for providing the service. Everyone can make an account easily and there is no limit on how many accounts can one person have. There is unlimited amount of data currently on servers.

Why is companies providing all this free?
Where does this huge amount of storage capacity come from?
Where is all this ‘infinity’ amount of data being stored?
What benefit do the companies have?
Will it be free forever?