It's certainly a commendable philosophy to protect the privacy of members, however, the return address in the header is used when one clicks on "Respond All" or whatever its called in your mail client. The address of the sender is right there. Also some members, like me, include an e-mail address as part of our signatures.
I think the purpose of the response is important. Certainly something meant is pure advertising is undesirable and anything insulting should result in the senders being removed from the list (I've have very occasionally gotten such messages but they are rare). Some members just don't want the extra messages.

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Richard Knoppow
dickburk@ix.netcom.com
WB6KBL