I sure hope there's more to it. Imagine this example:
Taxpayer A earns more than $3,000, but falls just below the standard deduction and exemption amounts, has no withholding and does not need to file a 2008 tax return. During the summer of 2008, Taxpayer A receives a $600 tax rebate check. Since Taxpayer A is not required to file a 2008 return, Taxpayer A does not have to pay the $600 back.
Taxpayer B makes $100 more than Taxpayer A, just barely causing them to have taxable income of $100. They had no federal withholding on their paychecks. Taxpayer B receives a tax rebate check of $600 during the summer of 2008. Taxpayer B files a 2008 return, indicating they have $100 taxable income, resulting in federal income tax of $10. Taxpayer B has to pay their $10 tax, plus their $600 tax "rebate", for a total of $610 back.
I hope if the article is correct, those whose acutal tax calculated is less than the amount of their rebates will not have to pay that back in. The other concern I have is for large young families, where maybe dad goes out to work, mom stays home with the 4 kids, and suddenly, they could receive a tax bill that causes them great financial distress.