The simple truth is that people are allowed to lie, as long as they don't do it while under oath. If the lie is egregious enough to be damaging, then there are existing laws in place to address it.
The problem with attempting to regulate the internet is determining where one nation's influence ends and another begins.
Lets say I make a web page that reads 'Barack Obama is related to gophers' - an obvious lie..
What if I buy webspace that is hosted on servers located in the United Kingdom ? France ? Japan ? Where does the rights of The United States to exert its influence end ?
..And the primitives thought Bush overreached.. Team Obama wants to make the 'Thought Police' a reality.