MONEYWEB LIVESTREAM A key source of revenue for the sector. By Ryan Vlastelica, Bloomberg 11 May 2021 08:04 Image: David Gray/Bloomberg Alphabet and Facebook tumbled on Monday, leading a broad move lower in internet stocks after Citigroup warned about the outlook for digital advertising, a key source of revenue for the sector. The firm downgraded both names to neutral from buy, writing that âcaution is in orderâ for companies that derive revenue from digital advertising. While ad budgets are expected to continue shifting online, growth is likely to decelerate, and âhistorically, that usually isnât bullish for multiples,â analyst Jason Bazinet wrote.