RuleReevaluationBehavior has been supported in WF Rules since .NET Framework 3.0. It is an enum that you can tweak to control forward chaining and the re-evaluation on a per rule basis. Typically this property is used to prevent infinite looping due to dependencies that the rule has, either on it's own actions or on other rules.

To learn more about this, please go to http://msdn2.microsoft.com/en-us/library/system.workflow.activities.rules.rulereevaluationbehavior.aspx or http://msdn2.microsoft.com/en-us/library/aa480193.aspx#introwork_topic5.

We are trying to find more about the usage of RuleReevaluationBehavior - if you are using it in your WF Rules apps, please email me (contact me through my blog) as I am interested in learning about your scenario. We are considering removing this knob and want to determine the impact and understand what kind of scenarios it is being used for today.