How is Allen & Company unlike other banks? Let us count the ways: It has no website, no barrage of press releases touting recent deals, no sprawling menu of financial services, no research division, no employment contact, and no formal recruiting process. What Allen & Company does have is a platinum reputation and serious mystique, earned over nearly nine decades of semi-secretive, exclusive advisory and wealth management work with some of the biggest names in corporate America. The firm is an institutional broker and money manager for high-net-worth individuals, including the founding Allen family; it also provides M&A, underwriting, and related advisory services.

Most of Allen & Company's clients hail from the media, sports, entertainment, communications and technology sectors—this tiny boutiqu...