U2 frontman Bono has seen his vast fortune slip by $342 million (£218 million) in the last week, according to NME's calculations.
The singer owns 2.3 per cent of the shares in Facebook through his private equity firm, Elevation Partners, which they bought for $90 million (£57 million) in 2009.
When Facebook floated last week, 2.5 billion shares were issued at $38 (£24) a share, meaning Bono's firm's 57.5 million shares were worth $2.19 billion (£1.38 billion).
But, as the week has gone on, Facebook share price has fallen sharply and is now $32.05 (£20.45), meaning Bono's firm's stake is now worth $1.84 billion (£1.17 billion).
The U2 frontman has taken steps to distance himself from reports that he has become the richest musician in the world, overtaking Paul McCartney with his new Facebook windfall.
He told MSNBC: "Contrary to reports, I'm not a billionaire or going to be richer than any Beatle - and not just in the sense of money, by the way, The Beatles are untouchable - those billionaire reports are a joke."
He added: "In Elevation, we invest other people's money endowments, pension funds. We do get paid of course. But you know, I felt rich when I was 20 years old and my wife was paying my bills. Just being in a band, I've always felt blessed. I got interested in technology because I'm an artist."
He continued: "Technology is huge, I wanted to learn about it. People might say that's odd, but I think it's odd if artists aren't interested in the world around them. I'm always chasing that. Facebook are an amazing team, a brilliant team, it's a technology that brings people together."
U2 are rumoured to be working on new material with One Direction's songwriters, according to reports, with Swedish pop svengali Carl Falk, who penned the boyband's "What Makes You Beautiful" apparently on board.
Thanks for the report to NME.com.