Lots of people trusted Christian Karl Gerhartsreiter. At least two women married him - though they each knew him by a different name. The members of elite social clubs in San Marino, Calif.; Greenwich, Conn.; and here in Boston embraced him and vouched for him. A series of investment firms offered him jobs as a stockbroker and bond salesman, even a vice president, despite his lack of credentials, experience, and, as quickly became clear, his at best rudimentary knowledge of finance. And over the last decade or so, neighbors and acquaintances have believed that he was Clark Rockefeller, a retiring, somewhat aloof man who implied, but never came out and said, that he was an heir to the Standard Oil fortune.