Apparently email has been used in the past to serve legal process on a person, but someone recently got served via the Facebook social network.:
Service of process is important because it gives the defendant notice that a legal proceeding is going to take place. Service of process protects “unknowing” defendants from getting sued (and losing because they didn’t show up) without their knowledge. But many people, like the Australian couple in the article, try to dodge getting served so that they can’t be sued.
For corporations (and other legal entities), the registered agent is the person who will accept service of process on behalf of the corporation.