Before Gmail's launch in 2005, the most popular choices for web-based email were Hotmail and Yahoo!. Then Google made a splash with its webmail offering that did away with folders, introduced threaded messages, all with very generous storage quotas.
Now, more than six years after, Google is ratcheting up its effort to steal even more users from those other services. Google typically lets its products speak for themselves, but the new "Email Intervention" webpage put up by the company is clearly aimed at capturing those who are still on some other mail service.
It's a bit of a cheeky move, but don't forget the in terms of worldwide numbers, Hotmail and Yahoo! Mail are ahead of Gmail.