SFI banners work. It's a numbers game so the more exposure a banner get's the more relevant it becomes. Traffic is the name of the game. You need to get visitors to see your banners as often as possible. To do this, you need to place the banners on traffic exchanges that have 100,000 members and more. Placing banners on obscure sites is sure to be a failed strategy because they don't have the traffic needed to get PSAs.