How To Use the “Seven Deadly Sins” to Turn Visitors into Customers

Good article - with regards the first point - Sin #1: Pride - "Showing off your customers. People want to use tools that big brands use." - Would you need to get permission off of the big brands to use their brand on your site ? Or the fact they use your site - could that be enough to publicise it ?

Are there good examples of sites that use virtue rather than vice to be sticky / viral? There's something depressing about it being a successful strategy.