Just got my invite for FireEagle.
FireEagle touts its privacy controls, one of which is to allow the user to temporarily hide their location from any and all otherwise authorized applications.
Similar to the 'Break Glass' use case for medical emergencies, this scenario is known as the 'Red Light District Vacation' use case.
Another mechanism allows the user to purge the Yahoo! database of their location info
With respect to the final caveat, why not? This permission page for authorizing Dopplr to access FireEagle makes it clear that applications can both read and write.
So presumably FireEagle itself doesn't expect the applications to themselves offer up endpoints to which FireEagle could send a 'purge' message.