Like hacking and the like, spamming is very profitable an activity, especially when linked with stock trading. According to this article, £1.5m in one summer, more than the salary in one's life time for most of us; and guess where they are coming from, sadly? Russia, HK and Canada, highlighting a constant feature of cybercrime, i.e. it is global crime.
The article does not hint on how the investigation has been done, but i'll be curious to know if the stock exchanges internal police were involved...
"US indicts pump-and-dump 'spam king' " (4 January 2008)