bitcoin is not an efficient market either... and it could all come tumbling down tomorrow as real researchers with phd's have pointed out. but it hasn't; at least not yet.
people are already trying to game the system... this was discussed a while back I believe it was someone who calculated that confirmation power of 3 bitcoin confirms equals 2.5 for mastercoin. (i'm recalling this from memory so someone feel free to look it up and correct me) anyway so one simply needs to wait 7 or 8 blocks, the role of the protocol does not include enabling high frequency crack trading.
This was said by JR in a debate with killerstorm on reddit. I don't think there has been meaningful research done on it.
user currencies are separate in the spec from smart properties which could be stocks, bonds, etc.
Ah OK I misunderstood the nomenclature then.