Most people talk about the cost of spam as just the time spent
hitting the "d" key. However, there are two much darker
consequences. First, people change their online behavior to make
themselves less accessible by e-mail. For example, just in the last
week I got two requests from people to take their email addresses off
articles posted to Advogato. Many people believe that the purpose of
email and the Internet in general is to foster more open
communications. Spam makes it less so.
Second, overagressive spam filters sometimes cause serious difficulties.
Here is one recent example:
Entities like SpamCop would not be necessary if it weren't for the
volume of spam, and they certainly wouldn't be able to shut people's