Spam clogs servers, chokes network bandwidth, saps the productivity of IT and non-IT staff, and makes it harder to use e-mail effectively. However, the real impact of spam may ultimately be subtler and more damaging than just the technical or productivity problems it causes.Left unchecked, spam may end up reducing the effectiveness of e-mail by making some users so hypersensitive that they are no longer willing to receive potentially useful content.At the recent Institute for Spam and Internet Public Policy conference, Guy Kawasaki correctly noted that receiving spam may be the price that we all have to pay for not missing important e-mails, since it\u2019s far better to receive lots of what we don\u2019t want than to miss the critical information we do want.Put another way, is it better a) to assume that everyone\u2019s a spammer until proven otherwise and thereby realize productivity savings from the reduced flow of inbound e-mail, or b) to potentially miss important e-mail from prospective clients, the press or others with whom we\u2019d like to establish a relationship?For example, we recently called an individual asking for permission to send him an e-mail message. After receiving his blessing, we sent the e-mail, but it bounced back with an indication that our e-mail was unsolicited. We then sent e-mail to the administrator (as we were invited to do in the bounce-back message) explaining that we had received permission via telephone to send the e-mail - to which the administrator replied that the spam filter had been modified so that we could resend our message. We did so, but the original recipient immediately replied to his administrator (and copied us) that our e-mail was unsolicited, that our e-mail address should be removed from his company\u2019s approved list of senders, and that our domain should be blacklisted. All of this within a few days after we received verbal permission to send a single e-mail.Of course, all users and enterprises should protect themselves from spam by implementing good spam-blocking technology and doing things to help keep valid e-mail addresses out of the hands of spammers. But to reach the point where one assumes that everything is spam - whether it\u2019s a single, personally addressed e-mail message or an advertisement sent to a million people - means that spam may ultimately change the perception of e-mail as a valuable business tool in the minds of many. The perception that e-mail is no longer as useful as it once was may end up being spam\u2019s ultimate legacy.I\u2019d like to get your thoughts on this issue. Please drop me a line at mailto:email@example.comI promise I won\u2019t add your domain to our blacklist!