Shares in Zynga, the online games company behind the Facebook favourite Farmville, fell 5 per cent on their first day of trading on Friday.

This was a good week for bank bashing.

Royal Bank of Scotland, Barclays and HSBC were among 17 giant banks sued last night by a US government agency, seeking billions of dollars in compensation over their packaging and selling of mortgage bonds in the run-up to the credit crisis.

Bank of America, the US financial giant which acquired Countrywide, the nation's largest subprime mortgage lender, at the peak of the credit crunch, will pay $8.5bn (£5.2bn) in the biggest-ever settlement of claims over toxic mortgage bonds.

New US regulations designed to make financial markets safer and prevent a repeat of the credit crisis could in fact kill off a major part of the secondary market in loans and leave housing finance reliant on government support forever, representatives for Wall Street's major firms are warning.

The former chief executives of the US mortgage finance giants Fannie Mae and Freddie Mac could become the next senior figures facing fraud charges, as regulators pursue wrongdoing in the lead up to the credit crisis.

Withdrawing federal government support for the US mortgage market could wreck the economy and leave US house prices moribund for years, a leading bond fund manager has warned the Obama administration.

US Outlook The US is back on Bailout Red Alert, and this time round the federal government looks like it might have to pay to bail out – itself. No one should be surprised to learn that the Federal Housing Administration has found itself facing big losses, what with so many Americans failing to pay their mortgage. Republican politicians scent a scandal of Fannie Mae and Freddie Mac proportions, and are already making hay, but this is no time for the Obama administration to go defensive about its support for the US housing market.

The US government borrowed more than ever in peacetime last year – some $1.4 trillion, said the Congressional Budget Office yesterday. Proportionately, the deficit is one of the largest among the advanced nations – 9.9 per cent of GDP. Loss of tax revenues during the recession, the costs of supporting the jobless and the extraordinary scale of public support for the financial sector have all driven the deficit higher. However, the latest news on unemployment suggests a slightly brighter outlook.