Honesty of Spammers
A few weeks ago I decided to try an experiment. I have a Yahoo email that I give out when I am asked for an email address when registering on web sites, etc. Not surprisingly this account started receiving quite a bit of spam.
My experiment was to see what would happen if I told the spammers to take me off their list. So for 2-weeks I clicked on the "take me off your list" link of every spam I received ... or at least the ones that provided a link.
The result was that the amount of spam I was receiving tripled. So if anyone is in doubt about replying to spams in order to get off the list I can tell you it doesn't work.
I guess I should say that some "reputable" companies (e.g., Walgreens) did remove me from their list, so if you know the spam is from a big company, then you can probably take the risk of replying. However, make sure the email is from the company and is not a fake address - for example if the name says "Walgreens" and the email address is something like firstname.lastname@example.org then you know it isn't really from Walgreens.
Also I would recommend the Yahoo spam filter. It is over 99% accurate.