the other day at our bank, while my wife and i were transferring some funds between accounts, we found that on one of the accounts, a phone number that has no relationship to either of us was listed as being her personal contact number. the bank officer seemed to be unaware of how this might've occurred and didn't seem particularly alarmed by it, but it made both of us uneasy, especially when later we did a google search of that phone number and on at least one website it came back as being associated with her as well...we tried calling the number but only reached an answering machine, so are wondering who might be the best person to contact to discover whether or not and to what degree anything malicious is likely to be behind the situation...
Most probably, there was some human error upon entry, probably by an anonymous operator at the bank. If the number is also on a Web site associated with your wife's name, then the most plausible explanation is that the bank sold some of your personal information to third parties, as they are prone to do. Have you ever wondered how all the people who call you in the evening to sell you new windows, subscriptions to magazines, or eternal salvation, obtain your name and phone number ? Well, wonder no more: they simply buy personal information from companies and other institutions who have it. Information from banks will be especially well appreciated on that market, because it can come with some annotations such as "tends to use credit cards a lot" or "filthy rich".
Whether banks (and other institutions) are morally allowed to sell your information is an open debate; but legally speaking banks tend to be well-covered.
In the case of your wife, the error on the phone number should be fixed because, unfortunately, some banks use the phone number as an identification element. But as soon as the number is fixed, this particular vulnerability is removed (at least as much removed as it can be). Otherwise, look at your bank accounts to see if anything weird occurred; if nothing is wrong, then you can cease to worry.