It was bound to happen -- an abstraction library to hide the differences between mapping APIs: Mapstraction. It's a collaborative effort initially funded by the UK property finder Nestoria. As they describe:
Mapstraction additionally fills some holes each provider's current offerings (taking advantage of existing open source solutions where possible) to normalise the feature set across platforms. In the future, Mapstraction will also talk to OpenStreetMap for people who want to build maps without restrictions on derived works.