I get some “Forwards” that contain more than 50 email addresses. I would think spammers would love to get their hands on those.
Wouldn’t it help reduce spam if people would remove the previous address before sending the FW:? This can be done with a simple click in most mail systems. And send all FW:'s as Bcc, (Undisclosed Recipient).
I always do all the above.
Most spammers get your email from places it has been posted on the internet. This may include newsgroups, message boards, web pages, etc. The spammers have crawler bots that search web pages looking for email address.
They can also get it from internet sites that you gave your email address to as some part of a registration. Some companies will sell their list to their “marketing partners” and those partners will spam you.
So it would only be worth it to remove the Fwd list if the email was going someplace that a spammer could find it. For example, if you are on a mailing list where the archives are put on the internet, then it may be worthwhile to remove the Fwd list. But if you are just emailing between friends or coworkers, then it probably doesn’t matter.
It is also a matter of common courtesy to hide email addresses from the other recipients. Personally I do not mind getting things sent to me, but I do not want 50 other recipients to get my email address. Bcc is very easy.