Machines took over

Stock Exchange plunges...because the machines took over

However, others said the stock volatility could have been exacerbated by electronic trading issues rather than worries about Greece.

'Machines took over'

"This is an electronic market where bids can be cancelled at the flick of a button, and everyone cancelled at the same time," said Joe Saluzzi, of Themis Trading in New Jersey.

"We should be down big today, but not 1,000 points. This is an equity market structure issue, there's no major problem going on."

Computer trading is thought to have cranked up the losses, as programmes designed to sell stocks at a specified level came into action when the market started falling.

"I think the machines just took over," said Charlie Smith, chief investment officer at Fort Pitt Capital Group.

"There's not a lot of human interaction. We've known that automated trading can run away from you, and I think that's what we saw happen today."

Does this not scare you? It sure scares the hell out of me...