I love arbitrage situations, as it usually means someone messed up somewhere and you get to 'stick it to the man' :-)
It worked really well in the old days when you could do a triangle of currencies, but the internet and instant quotes kinda killed all that.
The only place I can think of now that still offers arbitrage opportunities is sports betting sites, heard of a few people still making money from that (while they can).
Thanks for the informative post, was interesting.