Terrorists have been using the Web - most recently, Twitter - for years (see my "Dark Side" chapter of New New Media). And the FBI and other agencies should continue to do all they can to root out this and other illegal activities online. But granting the President emergency powers is not the way to do this. Think about what Richard Nixon - who tried to dictate what the New York Times and the Washington Post could publish, under the guise of national security - could have done with such power, had the Internet existed in his day.
The balance between doing our all to combat terrorism, and keeping our freedoms, is not easy to achieve. But certainly we don't want to reward terrorists by turning into the kind of society that they embody, by fulfilling their goal of killing our democracy, from the inside. Google and Comcast have given us no reason to think they would not cooperate to the utmost with any national security needs - just as no newspaper in the United States has ever published information on troop movements that endangered their security. Whether we like the President or not, giving that office the power to control the Internet would be a dangerous blow to the political and personal freedom of expression currently enjoyed to a greater or lesser degree by all media in this country, and clearly guaranteed by the First Amendment.