Hello Andrew--interesting post of yours. I'm not sure whether the underwriting issue can be classified as either reasonable or unreasonable, but I do think when it takes hold, positioning and "sense of company" may be as important, or more important, than the realization of profit for participating organizations.
Somewhere a long time ago in this blog, I commented on what the whole underwriting notion can mean to corporate positioning. Rather than searching through the blog, let me see if I remember what I thought. The way I see it, as one or two companies decide to get gonzo and underwrite a site--say an auto-repair discussion--what would the draw be to subsequent underwriters? Well, besides giving something "more" to their customers than bland corporate speak and their own obligatory corporate web site, it would seem that underwriting a discussion like this could give companies an opportunity to gather into micromarkets of their own... to position themselves with organizational like believers. Don't minimize this potential phenomenon.
How great would it be for a smaller company to underwrite a site and be seen along side its well-established household-name counterparts, sharing an inherent interest in supporting the underwritten group? What an opportunity to stake a claim on what your company stands for (and doesn't stand for). Likewise, how quickly a big stodgy company seeking to change what it's about could become "cool" by underwriting the same auto-repair site with nimble net companies.
So to me, the follow-on benefit of driving profit, though I think that benefit will come, won't be the initial benefit of site underwriting. The initial benefit will be a chance to turn the notion of positioning on its head. Instead of saying, "We are unlike our competitors because..." companies will be able to align with like-minded organizations of all types, implying instead (without beating us over the head with boring boilerplates), "We are like our fellow underwriters because..."
This is what I see as the inital benefit, followed by a more grateful customer base who reward companies they believe give a shit.
That's all for now. Punch holes as you will.