Public companies typically use transfer agents to keep track of the individuals and entities that own their stocks and bonds. Most transfer agents are banks or trust companies, but sometimes a company acts as its own transfer agent.
This could explain why whalecatcher got a letter from his bank.
Transfer agents perform three main functions: (I only included one) Issue and cancel certificates to reflect changes in ownership. For example, when a company declares a stock dividend or stock split, the transfer agent issues new shares. Transfer agents keep records of who owns a company's stocks and bonds and how those stocks and bonds are held—whether by the owner in certificate form, by the company in book-entry form, or by the investor's brokerage firm in street name. They also keep records of how many shares or bonds each investor owns.