Good points all around. We definately have to focus on keeping these SEO users on the site longer. More importantly, to have a good acquisition funnel to convert them to registered/regular users.
I'm not so sure all traffic is created equal, but the marginal benefit of all traffic is certainly positive.
To encourage users to sign up you just need to encourage more interaction / personalisation. Easier said than done, I know.
The news aggregation game is a bit in-and-out... traffic we receive (as a publisher) from aggregators comes in and mainly bounces. These readers often browse multiple sources to get a view on an individual story (to get a wider spectrum of views, more detail, better pics, more user insight etc).
The way NewsCred is designed doesn't lend itself so well to this... you have promote one story at a time; I'd consider adding more links to more sources on that story, Techmeme/Google News-style, to take advantage of this sort of behaviour.
Maybe users can ultimately choose their own sources, or NewsCred can choose for them, based on where other people are going. The key is in achieving a good depth of coverage, rather than just pointing people at the big media sites.
I'm not so sure all traffic is created equal, but the marginal benefit of all traffic is certainly positive.