Remember Burnham v. Superior Court? That's the one where a defendant was personally served in California while traveling there on business. The U.S. Supreme Court upheld personal service due to transient presence in the forum state ("tag jurisdiction") as legitimate on its own, without requiring any of the "sufficient minimum contacts" nonsense of International Shoe.
Here's a law school hypothetical for you: What if an officer of a foreign corporation is personally served in the forum state? Does that grant a court personal jurisdiction over the corporation? No it doesn't, said the Ninth Circuit Court of Appeals in Martinez v. Aero Caribbean.