This week the Guardian ran a special investigation into police surveillance of protestors, and the controversial term "domestic extremism". The main articles are linked here, although there are more on their site.

Doth I protest too much?
When police admit you could be put on a secret database for being at a demo, it's time to worry.

How police rebranded lawful protest as 'domestic extremism'
The term "domestic extremism" is now common currency within the police. It is a phrase which shapes how forces seek to control demonstrations.

Police in £9m scheme to log 'domestic extremists'
Thousands of activists monitored on network of overlapping databases

Policing demonstrations: Grounds for protest
"The real cause for alarm is that instead of being balanced by competing priorities of the public, the force's natural desire to extend its knowledge about and control over protests is being reinforced by changes in both technology and the law."

Activists repeatedly stopped and searched as police officers 'mark' cars
ANPR systems were first introduced to keep defective cars off our roads, but now they are being used to track and harass protestors with no criminal record.

Spotter cards: What they look like and how they work

Finally, Indymedia has a piece on whether the Guardian's stance is ethically consistent:
The Guardian on protest. Can we trust it?