I have been thinking for quite some time… I have a philosophy that may be Gmai is designed to make money - not only just Ads but also from end user once you finish up your 2 GB. Humm.. now the question is HOW?
You don’t have “Folders funda” in Gmail and space is just too much to delete even a silly forward … you need to be a communist to delete emails from GMail… couple of weeks back … i noticed that i have used 12% of my inbox, and i’ve using Gmail “actively” only for last 1 year or so… if I count myself an average internet user, after 8-12 years our Inboxes will be full, so that time we either must be delete old emails attachments etc or buy space from Gmail … third option will be to switch to other Mail provider but after using an email service for 10 years its almost impossible to switch… hummm…. and may by that time Yahoo! and Hotmail have signed off from there email services 
so signing up other free service will be difficult… may be by time we will be rich enuf to pay for emails. Another thought process around this is whatif I don;t pay GMail and keep using it… humm.. may be they abandon you from using other Google services (just image number of services from Google after 10 years… they may even go forward to Yahoo! in terms of number of services..)
May be Google planned to earn money like this after 10 years of so.. and its going to be recurring…. just image every email user (may be by that email and Gmail will be synonyms) paying $2/month to Google … 150Mil=> 300 Mil/month … sounds good amount of money … even for Google ..
