SIR RICHaRD BRaNSON and the billionaire family behind Wal-Mart are among a group of investors who stand to lose up to $1.5 billion (?930m) after the collapse of a large american solar panel firm.  Solyndra went bust last week, causing a stir in america. President Barack Obama made a high-profile visit to its California plant last year after the government lent the company $535m.  The failure highlighted the dramatic shifts in the industry that have sent several other once high-flying firms into administration.  Tom Murley, head of renewable investing at HG Capital, the private equity firm, doesn't expect Solyndra to be the last failure. "Prices have come down ferociously, and there is a glut of manufacturing globally," he said. "There will be other [bankruptcies]."  Since 2008, the average price of solar panels has dropped from $4 a watt to $1.30, a twothirds decrease, according to Bloomberg New Energy Finance.  The reduction has been driven mainly by a rapid expansion of supply from China, where many solar panel manufacturers can get cheap government finance.  Indeed, over the period global manufacturing capacity more than tripled, from 10.8 gigawatts a year to 33GW. The problem is that just as the industry geared up, governments reduced the subsidies companies were counting on to keep the orders rolling in.  Spain was once the largest solar market in the world. after the cash-strapped government slashed subsidies last year, new projects dried up. Italy is about to do the same, while Britain cancelled a generous tariff regime before it