This is something 95% of b2b startups don't consider (we certainly didn't). The epic win in b2b software is finding a SCALABLE way to generate leads. Word of mouth and PR are awesome, but they don't scale in the sense of "insert $1 in marketing spend here, out comes $1.10 in profit". It isn't sexy, but the scalable stuff includes cold calling, list buying, adwords, etc.
My gut tells me Feedback Army ought to raise their prices so there is room for them to still make many when they pay for leads. If they want to grow FAST, that is. Word of mouth can fuel pretty solid growth-- but you can't scale it on demand.
Related: $15?! That's crazy low. The author needs to A/B test pricing and read http://www.joelonsoftware.com/articles/CamelsandRubberDuckie...
I also once heard that the thing that made Art.com into a huge business was buying the pottery barn list, cross referencing it with new home buyers, and sending catalogs to the resulting list.
We've never done it-- but I don't think it's universally a bad business decision.