Google is the starting point on the internet for many users, Xobni is not. And, in any case, it's not a fair comparison.
That said, Xobni is a kick-ass product as a plugin for outlook and can be extended to the web ala plaxo and integrated as an overlay with any other social network.
In a more generic sense, the next google will probably not be the one everyone talks about, it would be the one people start using -- anyone remembers how people started switching from altavista to google?