If someone wants to post his music videos or extracts from his books or whatnot, that's fine. It's still "sharing thoughtful information and conversation." Posting links to ads for his homemade soap or artisanal cheese or microbrew isn't so okay, because it's not "sharing thoughtful information and conversation." Purely commercial spam links probably aren't going to get much attention anyhow. Really, I'd be more concerned that, if Hubski grows large enough to attract general interest, it will also attract PR flacks promoting their clients' agendas while pretending that they're just "contributing to the discussion."
Really? I don't think it's difficult to discern what kind of agenda a particular post has. Especially once a user has developed a pattern of submittals, it becomes clear pretty easily. I think the majority of people on here know when they're being sold something.
;)