Using a mailto link is a marketing idea that is a blast from the past. We've seen websites use mailto links for the purpose of displaying a contact-us link. Commonly any email address will be rendered as a mailto link for mobile or desktop websites. Read this great write up on OkDork.com
A twist on this is to eliminate the To and leverage the Subject and Body for prepopulated "forward to a friend" emails. Going one step further we can add a URL shortener to keep the link text small and in some cases get stats aggregated when your recipient chooses to forward the email using your link. Watch a half naked Noak Kagan step through the process manually.
This form eliminates the friction of producing mailto links and tags on a bit of URL shortening sweetness just for fun. Many URL shorteners will not support mailto links. These have been hand picked as shorteners that are mailto friendly.
This is a work in progress and improvements will follow as they are suggested.