I just spotted an advance fee fraud pitch in the spamtraps that started out with the greeting: Dear Trusting Friend.
I suppose the scammer could have meant “trusted friend,” which is still odd for an introduction, but makes a little more sense. Of course, if you take “trusting” to the extreme—i.e. gullible—you’ve just described the type of mark they’re looking for.
As a bonus: only two* of the ~270 Google hits for the phrase is not a reference to 419-style letters using the same opening. People just don’t write things like that normally, which makes it a pretty good indicator.
*I didn’t look at all 270, but there were only 30 hits by the time Google filtered out duplicates. And most of those were clearly recognizable just from the excerpt on the search results pages. For the record, both of the two non-scam hits used it as a description, not a greeting.