Some interesting advice in there. I especially like the part about "not being afraid to pay for users":
Every, and I mean every, acquisition channel costs money. It is just a question of whether the cost is direct or indirect. Channels such as PPC obviously have a direct cost. However channels such as SEO and Viral are commonly seen as "free" channels. They aren't.From http://onstartups.com/tabid/3339/bid/82788/Building-It-Is-Not-Enough-5-Practical-Tips-On-User-Acquisition.aspx