@il: Thank you, this is really insightful content.

I might be digressing here, but since you've offered to answer a few questions, here goes - I'd love to know what categories / sites I want to be looking at if my product's a small business CRM (like Highrise). To be more specific, it's a CRM tool that integrates deeply with Google Apps.

Maybe it's just me, but identifying a list of target categories that fits your audience well seems just as hard as optimizing the spend, especially when the audience isn't exactly niche.