Start-up internet companies valued on their ability to attract “eyeballs”, public offerings by lossmaking companies, dozens of “me-too” websites copying the strategies of a handful of successes? It all sounds so late-1990s.

Silicon Valley is showing all the signs of being deep into one of its periodic over-investment binges. Based once again on the consumer internet, this one is displaying many of the hallmarks that characterised the dotcom boom.