In the early 1990s, my boss and I fell victim to one of these scams. The bounty: $25M. It was via snail mail and faxes, all directly from Nigeria. We faxed docs over there also. After several months and multiple communications, we agreed to meet in a neutral place (London, England). I traveled, met one of their reps who, I believe, thought I was not worth their time and effort, and never saw him or heard back from them again. I invested time and money (mostly for the faxes), but my reward was to visit Europe on expenses paid mostly by my boss!