There are times when I want to give someone my email address, but worry about where it might end up and whether it will become another source of SPAM. In the past, I've created my own disposable email addresses by simply creating an alias specific to the purpose, knowing I can delete it if it ever becomes a problem. People without access to the email alias file on their mail host use Yahoo! mail and Hotmail for the same reason. A large percentage of the email addresses on my newsletter are Yahoo! or Hotmail addresses. I recently discovered a more convenient way to create disposable email addresses.
Take a look at SPAM Gourmet. They have a free disposable email service and a convenient way to create email addresses without even visiting the site. Once you've signed up and gotten a username, you can create email addresses with the format:
randomword.#.username@spamgourmet.com
The random word is anything you choose. The number is the number of times this email address should remain usable. The username is the username you created on SPAM Gourmet. You simply make these up at whatever site happens to be asking for your email and the first time someone sends email to it, the email address will be created and the email will be forwarded to your real address. After the number of emails you specify have been forwarded, the account is redirected to the bit bucket and any email sent to it is thrown away.
This is very convenient and useful. There are a number of other features such as being able to set whitelists for addresses, reply address masking, and the ability to see statistics on the email addresses you've created. Of course, if everyone used the same system, the spammers could just start creating their own email addresses to reach you. The service let's you set keywords that must be contained in the random words to help thwart this.
I wonder why more enterprises don't set up a disposable email service for their employees. If it were convenient to use, employees could generate disposable email addresses whenever the need arose and the enterprise could throw away any email sent to them after their usage period expired. I don't know how effective it would be, but its so cheap and easy to do, that its almost a no brainer.
Another idea would be add code to Mozilla so that whenever a user types #random# into a field, the browser automatically goes out to a service, retrieves a generated disposable email, and substitutes it in the field where #random# was. This would make it trivial for browser users to use disposable email addresses.