Here is how it works.
1.Legal to mail. Please obey the law, of course.
2.Has no identifying information. No need increasing the risk of ID theft.
3.Will not hurt the people who have to open this stuff. The point is not the make their job harder, but to make the companies pay for the inconvenience to you and to use their own scam to do it.
4.Potentially educational. Sometimes I receive political or religious stuff to which I object. I like to use those SASOs to send them back information on abortion rights.
5.The bigger the better. Use tape if you have to. I think they not only pay more for weight but also bulk. Not being an expert on bulk mail or credit card company operations, I could be wrong.
Don't spend too much time at it and only do it if it brings a measure of satisfaction. I can't guarantee it will stop the offers - it's really just for fun. However, my dad says he did it and after about six months the offers stopped. Unfortunately, that's about as credible as the "guy" who shared the idea on the radio.
If anyone can debunk this sweet means of revenge, please do so gently. I would be sad to lose my revenge on companies who prey on the poor, deceive their customers, enable ID theft (partly by sending those damn offers) and then want you to pay extra to "protect" your account. If anyone works in the mail room of a credit card company and thinks this is hurting them personally, please let me know.
If you take this away from me though, please be prepared to provide me with alternate sources of fun revenge. If, however, you plan on just saying nasty things about wasting my time doing stupid stuff like this I say, with love, stop reading this because you're right, you're wasting your time. I also say, I do a ton of other "productive" stuff but also need a nice outlet for some pent up sassiness. If you don't, you are a better person than I.