So the spy would be

• The new guy who's always going on about the need to forcibly overthrow The System(TM), who openly sympathises with direct action and always wants to have a piece of the action.

• The disaffected long-timer who wants to distance himself from the community in order to ease his passage back into normal life.

• The guy the cops have in a tight spot over some entirely unrelated issue (drug issues, petty criminal activity, etc.) who cuts a deal.

- Jake

If you only spend 20 minutes of the rest of your life on economics, go spend them here.