LessEverything.com - created everybodyhatesquickbooks.com to gain a few users for their account app lessaccounting.

HashRocket - cofounder wrote a book on ruby & now runs a kickass consultancy.

IMO, you should market in every way you can possibly afford; adsense, pulse360, adblade, ysm, ad center, ad networks, retargeting, viral websites, viral videos, email follow ups, affiliate marketing, coreg (think appsumo) & traditional PR. Take every avenue you cam afford & pump it for paying / profitable users.

PS: Good post Mark!