Why is it difficult for governments to censor information on the Internet?

What will be an ideal response?

ANS: Because the Internet is global, and the information that one country find offensive might exist on a computer in another country, where the laws are different. That's what happened when a French court banned the online auctions of Nazi memorabilia and demanded that eBay remove the items (it refused). This is also why the U.S. music industry has been unable to stop file-sharing services located abroad.