I'm genuinely interested in the following question: why would anybody think that spam based advertising works? I'm not in the business of marketing so I have n

I'm genuinely interested in the following question: why would anybody think that spam based advertising works? I'm not in the business of marketing so I have no idea whether this is common practice in the business, but just looking at the way I (and the people I know) interact with their email clients, it seems to me that unsolicited mail ads achieve nothing. They may even be harmful to the business: I don't receive much of these thanks to gmail's excellent filter, but I know that it would really annoy me to receive unwanted ads..