Most of the anger at PRISM is that it apparently involves collecting data about everyone.

Carnivore was supposedly designed to be deployed against people who are suspects for a particular reason already. While some of the ECHELON satellite intercept hardware and the existence of the UKUSA agreement is known, exactly what is intercepted does not appear to have been ever leaked, and so the public have never had any reason based on mainstream media reports that they personally are being spied on.

Many people might be happy for a scheme that involves criminals being monitored, because they never think it will apply to them. But those same people will be angry when they hear definitive proof that a government is filing away data on them even though they didn't do anything wrong.