HPE Source address validation (SAV) covers the general techniques to prevent IP source address spoofing, which is often used in networking attacks. Two primary problem spaces addressed in work on SAV include building the "source of truth" for what IP networks should be permitted to source IP traffic behind a set of network interfaces, and implementing the data plane enforcement for the validation. Implementing data plane enforcement, especially for inter-domain networking for the Internet carried by BGP-4 [RFC 4271] has a number of scaling considerations. One consideration is the potentially large and often asymmetric sizes of the per-interface SAV tables vs. the Forwarding Information Base (FIB). A second consideration is synchronization issues between SAV enforcement mechanisms and the forwarding state for the FIB where a lack of coordination may result in dropped or mis-forwarded traffic. This draft explores these two considerations under the title, "The asymmetric contract, and the broken promise."