tedster - 6:27 pm on Oct 13, 2010 (gmt 0)
A lot of B2B companies are in the same boat, Husky. From what you've outlined, it sounds like there *might* be some value from interaction with (especially) the architectural practices segment of your market.
Would interaction with them be valuable on Facebook? Maybe not - but there's a lot more to social media than FB. These folks sound like true "influencers". Do any of them blog? Tweet about the industry? Post on industry forums or comment on industry blogs? Just listening might be useful, even without interacting.
As you say, it definitely takes time and resources to engage on social media, and there is an expense involved in that. So it is a business decision. And it can be difficult to quantify the benefits, even if listening to your marketplace does give you a big business insight.