There's a local coffeeshop. They host shows, including a band a friend plays in. I've seen them there twice. This was also where I saw Chaconne Klaverenga.
They have a mailing list, through which they announce their upcoming events.
I signed up.
When the first mailing came, it came to me, to Johnny, to Clem, to Jenny, to Anne, to Trey.... Basically, there was a big list of email addresses, and she put them in the To: line of Gmail and pressed send.
And now I have dozens of email addresses of people that I could now spam, if I was the scum of the earth.
Here's the trick – BCC. It stands for Blind Carbon Copy. If you send something out with someone BCCd, that person receives it without it being addressed to him. If you send something out with two people BCCd, neither can tell that the other was sent it.
Subject: My Coming Midwest Tour!
From: Sans Direction <email@example.com>
To: Sans Direction <firstname.lastname@example.org>
BCC: email@example.com, I_know@gmail.com
Just a tip from your old friend Sans.