This is definitely true, but the assumption is that long-term active users to a sticky portal can be monetized--it's just a matter of figuring out the best way

This is definitely true, but the assumption is that long-term active users to a sticky portal can be monetized--it's just a matter of figuring out the best way to do that. And the distinction of a destination vs. a tool seems like a valuable one. Google knows this, which is why they are pushing Google+ so hard.