Fair enough; again, it's probably not useful at every company, but in the companies that I've worked for in the past (big and small) that have used internal social networks (like Yammer for example), it's definitely been beneficial to me.
I think that wikis and shared network drives don't work as well for sharing content in the same way that they don't work for me sharing with friends. People like the format of a social network, curating content and sharing it with the right people in a way that it will pop up where they are looking and provide an easy way to have a discussion about it. And this sort of content shouldn't really "leave the net" (unless you're talking about the physical intranet); the idea behind this feature is that it stays within the company's control, in a place viewable only by employees.
To respond to your other points:
1) An interesting point, and this is where I think it depends on the company. I don't really view Google+ as a time-wasting site (though I do moreso with Facebook), because Google+ has a big focus on sharing interesting and relevant content to the user. In a company that embraces this sort of internal sharing of content, I think it could be very useful.
2) Perhaps lots of places already have deployed solutions for internal sharing; Google is just providing another way (a way that is being actively developed and potentially already is being paid for by the company because of other Google Apps).
3) I used Yammer at a small startup once, and it proved to be a nice way to aggregate work-related content. But at really large companies that are willing to have their data stored with Google, I think this is even more useful because it provides a good way to communicate with people you don't know at the company, and a way to follow what is being said by the internal superstar developers.
I liked the second paragraph. It's possible that I have an inherent dislike (no pun here) for the 'social' format. It is to be, almost by definition, unprofessional and low quality.
Maybe that's what colors my view on G+ in general and a corporate version in particular. Have to think about it - hard to look past an assumption like this on a whim. :)
I think that wikis and shared network drives don't work as well for sharing content in the same way that they don't work for me sharing with friends. People like the format of a social network, curating content and sharing it with the right people in a way that it will pop up where they are looking and provide an easy way to have a discussion about it. And this sort of content shouldn't really "leave the net" (unless you're talking about the physical intranet); the idea behind this feature is that it stays within the company's control, in a place viewable only by employees.
To respond to your other points:
1) An interesting point, and this is where I think it depends on the company. I don't really view Google+ as a time-wasting site (though I do moreso with Facebook), because Google+ has a big focus on sharing interesting and relevant content to the user. In a company that embraces this sort of internal sharing of content, I think it could be very useful.
2) Perhaps lots of places already have deployed solutions for internal sharing; Google is just providing another way (a way that is being actively developed and potentially already is being paid for by the company because of other Google Apps).
3) I used Yammer at a small startup once, and it proved to be a nice way to aggregate work-related content. But at really large companies that are willing to have their data stored with Google, I think this is even more useful because it provides a good way to communicate with people you don't know at the company, and a way to follow what is being said by the internal superstar developers.