I like JetMech's idea about announcing intentions. This is consistent with how full size aircraft are flown at uncontrolled fields, and it works well in an RC environment as well. I've flown at fields where it's used consistently, and others where it is more "jungle rules." As you can imagine, the former is a lot more orderly, and it actually means people think about maneuvers in advance, so they can announce them. At the latter, like the field where I fly now, it's a bit more difficult. For example, a few weekends ago I announced "LANDING !" as I entered a downwind leg. I'm on short final when some guy decides to walk out on the runway...not announcing his intentions. I'd like to see AMA adopt the "announce intentions" as a tool to improve safety.

I think that if he was flying opposite the established flying pattern and hadn't announced his intention to do so, and thus giving you the opportunity to get out of the way, then he is at fault.