One of my clients is currently a victim of an over-zealous ISP
recklessly trying to implement rpf.
Assuming the provider is doing the right thing by filtering routing
announcements, and assuming the customer has done the right thing
by informing their provider of the blocks they _might_ announce
(either via irr or email, depending on provider) it appears the provider
is _not_ doing the right thing by adding exceptions to rpf to make
it semi-strict based upon this data. With this sort of setup, it wouldn't
matter if the customer actually was announcing the routes or not.
Anything, when used incorrectly can have bad impact.
The various implementations of RPF that I've seen allow for these
situations, they can't however hold the provider or customer's hand.