Joan - yes, that's why I challenged my friend for generalising in that way. But since I've also witnessed what she was saying at first hand on countless occasions throughout my life, I also had to sadly agree that I could see why she would interpret it as dishonesty.
Can I also say that I'm impressed by the way you willingly apologised for making wrong assumptions about me, rather than fudging some kind of half-baked justification? I have so much respect for people who do that, and it saves so much aggro. 
WhiteShores - I actually do the opposite of your friend: I am happy to tell people where I originate from in the hope that they'll remember the totally uncrooked Nigerian they actually met more than the crooked few who send round those dodgy emails.
Weirdly enough, I don't think I've ever personally received a Nigerian scam email! Is something wrong with me?! 
Though I've received plenty of scam mails which don't specify where they're from. It's always so obvious because either they're worded really badly, in crap English, or the situations they present are so unlikely, e.g 'if you are mugged at a cashpoint you should type in your pin number backwards and this will alert the police to come to your rescue.' 
Yeah, I can just see that working. But you can always double-check any suspected scams on websites like snopes.com.
Also scam mails are frequently sent as spam, i.e. sent to millions of people at the same time, using some kind of 'bot', ie. dodgy hacking technology about which I know nothing whatsoever. Hence giving the impression that there are millions and millions of people doing this, when the likelihood is that it's a relatively small number.