Clarification on social networking software

LinkedIn CEO Reid Hoffman sent me a detailed note over the weekend responding to my post on social networking services. 

He pointed out that LinkedIn’s new tool for uploading Outlook contacts
doesn’t automatically send an invitation to everyone in your address
book.  You have to select the people to invite from a list. 
Reid also noted that unlike Spoke, LinkedIn only considers someone a
connection if you have either invited them to establish a relationship
or accepted a connection request.  By automatically inferring
relationships from email messages you’ve sent and received, Spoke
generates a much larger network, but in so doing it includes many
relationships that really aren’t personal connections.

These are good points.  Reid is a passionate believer in what he’s
doing, and the design choices in LinkedIn have been thought through to
anticipate many issues that could arise.  (So have those in Spoke,
with different outcomes.)  However, my concerns remain. 
Social networking services are still least useful to the most connected
people.  And I’m still looking for a situation where one of them
provides me with some concrete value. 

I maintain an open mind on this.  I really want to see services
like LinkedIn,, and Spoke succeed.  (As well as services
that aren’t social networking but have similar elements, like SocialText,
where I’m on the advisory board.)  I’ll keep fiddling with these
tools in the hope they achieve more of their exciting potential.