Web overlords Amazon and Google have grown so fast that they arrived at the ‘what next?’ moment rather more quickly than most companies. Speed is uncommonly integral to the industry they inhabit but when it comes to sustaining growth, they have the same strategic options as anyone else. Expand or diversify. Build or buy. Amazon, the retailer, now wants to sell online storage and computing power. Google, the search engine, is squaring up to Microsoft with its own office software package. Can they pull it off? Because diversification, the route both are now taking, is never the safe option.

