The title of the world's most valuable company seems to be changing hands nowadays about as quickly as Australia chews through prime ministers, with Amazon the latest to have a crack at the top spot. The ecommerce giant's market capitalisation yesterday briefly surpassed that of Apple, which itself had been dethroned as the world's most valuable company last week by Microsoft. With shares up 4.7 per cent, Amazon weighed in with a market cap of $865.3 billion that crept a few hundred million above Apple, whose shares were up 2.1 per cent at the time. Amazon shares pulled back slightly to trade 4.4 per cent higher in afternoon trade, while Apple extended its advance to 2.7 per cent to reclaim its throne. Microsoft was up 1 per cent with a market cap of $860 billion while shares in Google parent Alphabet — still in the upper echelons of size — were 0.4 per cent higher. Microsoft in late November finally achieved a market cap that exceeded Apple's, marking the first time the iPhone maker's value had been surpassed since it took the baton from ExxonMobil in 2011… Earlier this year, Amazon joined Apple as the second company to achieve a valuation of $1 trillion, but its time in the club as second entrant was brief.