In usual form, Jim cuts right to the chase with some stats that simply prove what I believe to be the case that Facebook is first a foremost a social network, not an advertising network.
That is no comment on Facebooks business model. I simply question that merely because young people are your target market, that you can stuff traditional interruptive marketing techniques into FB, and they will work. Jim’s analysis proves that out.
NetbankerOverall, the banking and personal finance apps have anemic usage levels totaling just 263 daily users (for apps with more than 1 daily user). That does not include virtual currencies or stock tracking/investing applications (see note 2). In comparison, the most popular general Facebook app, FunWall, has more than 3 million daily users.
Bankwatch 
Potential bank customers are out there looking for you, and I agree Colin that incorporating Facebook into your marketing plan will help reach their demographic, increase brand familiarity, and convert to actual customers.
By establishing a Facebook presence banks and credit unions secure themselves as an “established” presence. They may seem anemic now, however; when online account opening becomes the norm, having an established social networking model will pay off in spades.