Why do they spend so much tracking activists?

Why do the CIA, FBI, and Connecicut State Police spend so much time tracking activists?

The Ken Krayeske arrest last week has caused quite a bit of good blogging, and finally, so far, some good inquiry by the Governor facing the threat and likely reality of legislative investigations. (For posterity I will remind you that Ken is a well known local political activist, peace activist, and campaign worker. He was arrested on what look like completely trumped up charges, by cuff happy local police, motivated with Kafkaesque fears by the State Police that Ken blogged that he might create a legal protest outside the Governor's inaugural ball)

Often, people seem to ask: "With all the foreign terrorists and suspected domestic terrorists and criminals, why do they spend all those $ and infiltrating and spying on peaceful activists and protesters?"

My answer maybe different than most. I recognize that paranoids and fearful people such as Nixon and Bush may be a huge factor, yet perhaps they are more enablers than causes.

Here is my partial answer:

You are a career spy or investigator. Over time it becomes less glamorous; just a job; a wife; children.

Would you like to learn Arabic? Find a way to look middle eastern? Put on a birka? Go to Iraq/Iran and live like the natives for a few years in infiltrate the country and try to find and link up with some possibly blood thirsty terrorists/revolutionaries?

Or would you rather disguise your self as an average American in the town where you family lives and infiltrate groups there, while you and your family live a normal American life?

Given that, would you like to infiltrate the underworld and start a career with Mafia, proving yourself along the way as you get closer to the blood thirsty leaders?

Or would go rather go down to your local peace group and join their meeting. Occasionally take one of those peace train's to NYC, and overnight bus rides to Washington D. C. etc.

I know which I would choose, and that's why I suspect there are lots of Homeland Security types who gravitate to this work.