Yep, I've been thinking the same, but there's always a risk. If the shares fall too drastically then there are several options. One is a takeover, in which case the shares would inevitably rise again; or there's other options: click here
if BP was looking to borrow large sums of money - which it isn't. That being the case, the credit rating change by one major agency is hardly likely to bring the company to its knees.
Don't run away with the idea that BP is a business heading for the edge of a cliff. The company is still receiving huge sums in oil revenues every day, especially as the current price of oil is in excess of the level that was budgeted for in the company's forward forecasts.
Yes, the share price has taken a big hit, but it will recover. In a worst case scenario BP is exposed to an aggressive takeover bid by one of the major names - Exxon springs to mind, and there would be than a touch of irony in that.