2012-10-05 UTC
# 
tantek tommorris, I think it's more like this: MetaWeblogAPI used XML-RPC, TrackBack used RDF (in model, philosophy, and implementation) and got spammed, Pingback was designed as a replacement in the context of being another "standard" blog API, and since the existing such standard used XML-RPC, it did too, for consistency with that API model.