Google's big opportunity
First, the thing to remember about Gmail is what a huge threat it posts to Yahoo and other sites. A huge percentage of the portals' traffic comes from email.
Second, what's with that logo? I know, this isn't a design post, but still.
Third, Google's big chance:
What if Google decided to make a Google account cost $1 a year, and you had to use a valid credit card to pay for it?
And further, what if your Google email address had to include your real name?
And third, what if a violation of Google's anti-spam rules (I'm assuming they'll have some) would cost $20 per incident?
Suddenly, Google mail would become a gold standard. People would happily let it through the spam filters. You could trust it. People would become suspicious of anyone who used any other non-google online email service... "what, you're afraid of validating your account?"
That's what I would do.