How Many B2Bs Out There Use Quora?

I've recently been poking around Quora to see if could be a useful tool in reaching a more professionally focused social media audience. But, I'm still on the fence as to its effectiveness.

In this recent chart on what social media platforms B2B marketers are currently using, Quora is coming in dead last...even behind Tumblr!

While I'm not surprised by the big 3 (LinkedIn, Twitter, and Facebook) topping the chart, I guess I am a bit surprised at the lack Quora-use. Is it just because the platform isn't very well known? I guess I hadn't really heard of it until a few months ago.

Are there any B2B-ers out there in the social sphere actively utlizing Quora, and what are the results? Good? Bad? Ugly? I'd love to hear. Thanks!