Perhaps the best link would have been to the full recap: http://www.craigkerstiens.com/2011/03/07/startupbootstrapped... which starts with SEO and addresses cost/value of other means.

Though also, many early stage bootstrapping products, at least here in the valley don't consider SEO within marketing. A key take away I'd suggest is that they absolutely should. This is all of course after building a kick ass product.