Prince Alwaleed bin Talal is the perfect investor for Twitter: immensely rich and willing to take a punt. Should Twitter be eclipsed by the next new thing and its value disappear, the $300m Prince Alwaleed and Kingdom Holding Company (of which the prince controls 95 per cent) paid would hardly be missed. His personal wealth has been estimated at $20bn, and the holding company lists $10.5bn in assets on its balance sheet.

Prince Alwaleed’s penchant for derring-do is reflected by his famous investment in Citigroup. But within technology and media, the prince’s focus seems to be on companies with big names that have fallen on hard times – including buying 5 per cent of Apple in 1997. Less profitably, he has put money into companies such as Compaq (now Hewlett-Packard), Motorola and Kodak. He also has made bets on rising tech companies before, including buying 5 per cent of Netscape for $145m in 1997.

Twitter is nothing if not up-and-coming: it has 100m users who log in at least once a month. The service handles 250m tweets of 140-characters every day. The issue for investors is how to turn all this wonderful activity into money. The company started carrying “promoted tweets” (read: advertisements) only this spring; eMarketer estimates that the company will have $140m in revenue this year, three times the 2010 level, and sees $400m in 2013.