Will the Olympic Games in Britain in 2012, on balance, prove financially beneficial?

Are quotes that the Games will generate about £2 billion for the economy realistic? Is it still a good thing to win the competition to host the Games? One effect of funding the Olympics in Britain is a reduction in funding for other cultural needs (for example, diverting the Big Lottery Fund from heritage projects to Olympic funding has reduced the money available for heritage by over £200 million). Consider the implications for tourism of such changes in funding.