Re: Didn't they read the bit about...
"But publicly traded companies are required to file their returns and statements with the SEC in an open transparent manner."
This is exactly the point. Which it seems some people are missing. It's one thing to lose money on shares because the company has failed to prosper. It's quite another to buy shares based on legally required information only to find out it's not true.
That part is not much different to buying a physical object that turns out not to do what the salesman told you it would.
If Groupon can be shown to have knowingly filed incorrect information, the company's future could be quite bleak.