I know that some people frown upon e-mail marketing, but I for one don't have a problem with it. The problem I do have with it, is that people abuse it by finding people's e-mails and sharing them in lists so that people can advertise to said list of e-mails. I think the proper way to do e-mail marketing is to get people to sign up for a mailing list, or opt in that is.
What are other bad ways of e-mail marketing that could ruin ones business and just annoy people more?