There is a way, but they need to do more groundwork. Facebook started University by University. Even if it's only people at my University that can use Facebook, that's OK, because I have something in common with those people. I don't need everyone else in my life to be able to use it in order for it to be of value to me.
They need to find groups of people who have something in common.
This could be University's, companies, sporting associations, etc. Anything where there is a group of people who have a reason to communicate with each other and where it can reach a critical mass of usefulness relatively quickly.
Of course, it will require a little more hand holding, but it will give the product a greater chance of success.
Use Buzz and Wave as examples.
I have absolutely no interest in interacting with my friends and family using those services. None. My Mum wouldn't even know where to start with them. They require too much effort. Besides she's got Facebook and everyone else she knows does too.
However, I would have happily given Buzz and Wave a go through my companies Google Apps account with the rest of the guys at my company. We try new services as a team all the time to see if we can find something that will help us in some way. BUT, these services were not available to me through my Google Apps account. Only through my Gmail account. Which is a bit of a PITA since -- at the time -- you could not be logged into both Google Apps and Gmail at the same time. So it was a non-starter.
My point? Facebook started small with University's. Students who had something in common. Google should probably start with businesses. Work colleagues who have something in common. Roll it out to one Google Apps account at a time. Hold their hand. Gain traction -- then with a solid base, spread your wings and jump.