Mark Zuckerberg went to an Italian restaurant yesterday and didn't leave a tip. Here's why this is no big deal.
Tipping is an American thing, to be honest with you. When you eat in an American restaurant, and have billions of dollars, you're expected to tip generously for mediocre food and service. Failure to do so will bring out the snark and the wolves. Waiters will even try to use social media to humiliate you.
In Europe, you don't really need to tip, depending on where you go. Zuckerberg went to Italy, and in Italy, you don't need to tip:
Here in Germany, if your meal is 32 euros, you pay your waiter or waitress directly and you can hand them 35 euros and they'll be very pleased with that, no matter who you are. They are paid, in most cases, a living wage and get benefits and time off. It's a solid, dependable line of work here. You won't get super rich, but you'll be happy with what some would call meager tips.
Zuckerberg sounds like a seasoned traveller to me, so calling him a cheapskate is a bit over the top.