According to the Missouri Information Analysis Center, the following people are considered potential terrorists:
Ron Paul supporters
People opposed to the Federal Reserve
Here is a commentary by Joseph Farah of WorldNetDaily:
Once the government started to ignore the rule of law and the Constitution under the guise of fighting “terrorism”, many defenders of liberty warned that this was setting a dangerous precedent. For while you might be happy to see the “bad guys” tortured and sent to concentration camps without due processes, you won’t be so thrilled when the government considers YOU to be a potential terrorist based on your beliefs.
The greatest threat to our freedoms is not from terrorists, Iran, China or Russian. The greatest threat has always been our own government. The Founding Fathers recognized this danger and created a Constitution with the design to limit the power of government.