Great post... Repeating theme here is "... I decided I couldn't afford the time/cost of [insert scalable marketing option] because our price point was too low."
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.
So many contextual factors go into making a decision for a business of any size. Some may consider a low price-point as a killer because it doesn't allow for scalable marketing. However, a low price point can help certain kinds of services get traction too. When Feedback Army launched its low price point was the topic of conversation.
I agree with everything you said, except for list buying. That's pretty much spam. List renting may be OK, but I would still avoid the practice. It's easy to damage one's brand with accusations of being a spammer.
It's all in how you do it. I know plenty of businesses that have gone nowhere but up buying good lists and emailing them in a personal-feeling manner (with clear unsubscribe instructions. It's not legally spam-- and if your audience isn't geeky, it's not generally going to piss them off.
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.