GuerrillaMail is an anonymous web service that provides you with a temporary email address—perfect for web sites that you don’t want to communicate with you but require email registration. Generate an email address and reload the home page to view any incoming messages. The 15-minute timer displays the amount of time you have remaining until your email address expires, but you can extend your time if necessary. The concept is not much different from previously mentioned 10-minute mail, 2 Prong, or the army of similar temporary email services—though GuerrillaMail even has a (paid) script to host this application yourself, which could come in handy if the guerrillamail.info domain name gets banned. Whatever service you choose, temporary email addresses can really keep your regular inbox spam-free.
This is useful when you need to be anonymous but I also know spammers use this for forums and temp email address to keep you from finding out there real email address or there real location.