Although it sounds good to stick it to a company that has hurt its customers, an investigation and penalty like this (a favorite pastime of headhunters like Henry Waxman) is a redundant penalty unnecessary to keeping companies honest and consumers protected in a free market.
Why? Reputation. Toyota has already lost millions in sales from its tarnished reputation. It has lost the faith of its consumer base, and millions of people in the next few years will think twice before buying a Toyota, which is a much larger cost than any arbitrary penalty anti-business congressmen can think up.
As economist John Lott puts it in his book Freedomnomics:
"...future profits are what a firm stands to lose if it cheats its customers. The potential loss of profits stemming from the loss of a good reputation helps keep businesses honest. This holds true so long as a business is concerned with its future profits."
How many moms out there do you think will be buying a Toyota any time soon?
To get a little more conspiratorial, it's interesting to note that General Motors (Government Motors) is more than 50% owned by the government, so perhaps the government is simply trying to kick the legs out of its non-union worker automaker competition?