oh lord.. 
Anyway... my guess is that it has something to do with opposite and (hardly) equal reaction to spam. Unsolicited means unwanted... period!
It kinda goes along the same lines as the use of what are known as whitelists (crossthreading-e). To allow traffic based on certain and only that criteria. (Almost) nobody (I know) uses a whitelist.
Something about this form of revenge works better when it is not personal (just like the problem to begin with). Cold, like revenge should be served. It's too much work (as well) to start typing in all the addresses I do want mail from... and what happens if I win the internet jackpot lottery... how will I know? If my *friends sends me an address from thier new location, do they have to *call me first to tell me the email is on its way?
This is why, on my network at work, my rule is: "Don't send/share files over the email system, send hyperlinks/paths to thier internal network location. Very few people have any reason to open files sent from other people... suspicion of the worst-case-scenarios keep people on thier *toes!
