Google’s new service seems to be catching on to a lot of users even before it’s officially publicly available. 10 million by latest estimation. Of course, checking it out is one thing, really buying in and sticking with it is quite another and only time will tell how useful the thing ends up being. Paul Allen, no not that one, the one who founded Ancestry.com, conducted the estimation and says that by this weekend, the number should be closer to 20 million. That’s a long way to go to catch Facebook’s 750 million, of course, but kind of eye opening for a service in Beta that just launched a couple weeks ago.