I'll bet a lot of these are inside jobs. The Securities Industry is a huge magnet for Psycopaths and Scumbags. I'm not exaggerating... People scoring high on standardized Psychopathy diagnostic tests... Like the one by Dr. Robert Hare... Make fabulous, productive stockbrokers and telemarketers... Precisely because they lack a conscience.
I remember someone raising this issue last fall on the Quotetracker forums which no longer exists ironically because of its deal with Ameritrade. Ameritrade said they dealt with the problem as soon as they found out about it. I doubt that. As I remember the poster who I assume was trading for a living had an email account dedicated to each of his brokers. The only party which had the address was his broker and that is how he immediately knew that his email information had been shared or hacked. He had contacted Ameritrade immediately but had gotten no satisfaction.
virtually identical to my story, which i posted here yesterday on another thread on the topic. though i wasn't the quotetracker person...and i only got more of the real story by talking with a techie about it on a followup call.