By Todd Bishop, GeekWire

So many people are on Facebook. How are they going to get them to switch? It’s going to have to be pretty great.

That was the immediate reaction from certain Facebook-addicted members of my family today as we read the blog post and watched the videos announcing Google+, the search giant’s (latest) big move into social networking.

The Google+ features themselves look interesting, offering a fresh take on social networking, at least. Circles is a way to group friends and family members into specific categories for easy sharing. Sparks is an “online sharing engine” that delivers content on specific topics for sharing with particular groups of friends. And “Hangouts” will attempt to bring a level of spontaneity to multi-person video-conferencing.

(For more details on Google+, click here.)

But the most important feature of any social network is the users themselves. And with more than 600 million of them, Facebook has a gigantic — and perhaps insurmountable — head start on that front.

Of course, Google has plenty of users itself, with 65 percent of the search market in the U.S., and an even larger percentage in some countries overseas.