If we had a good method for people to indicate routes that they didn't want to be aggregated, then more proxy aggregation could be done safely.
If I may... The idea of using a routing registry for this purpose has been suggested before. I still think it is a valid approach. Could be very useful in assisting with better proxy aggregation for all.
Let me just say I think the RR has some good uses, i.e. finding out what people intended the routing to look like, etc. I don't really understand how a RR can help with proxy aggregation seeing as the route objects really only provide origin AS and regular aggregation. It seems to me dual homed sites which are the concence of proxy aggregation, can be detected with a reasonably full set of routes, i.e. the second from AS from the origin in the ASPATH being different. (Or some split in the path outside of an AS communinity or confederation). But I don't fully understand all the details of this, so I'm sure someone can correct me if I'm wrong.