Bill Gates thinks Mark Zuckerberg "owes" him.
The 62-year-old business magnate - who is the co-founder of Microsoft Corporation - has been dishing out some invaluable advice to the technology entrepreneur since he launched Facebook in his university dorm room in 2004.
Speaking to The New Yorker newspaper, Gates said he regretted "taunting" regulators after he was accused of monopolistic behaviour 20 years ago and warned Zuckerberg to be more mindful of what was going on in Washington.
He explained: "I said, 'Get an office there -- now.' And Mark did, he owes me."