This is a great article, but keep in mind that the numbers are illustrative of one type of company. Mint was dealing with financial information, so they had to get "serious" fast and that means spending on things that, say, a Facebook or Twitter would not have had to spend. They project $30/per user for user acquisition (if I read that right), which again is very different for different kinds of companies, and different business models. Extremely high value niche companies would pay hundreds of dollars per user. On the other side Twitter being a mass player, would spend far, far less. Financial sites are valuable, so $30 seems like a good deal.