Blocked them many times but they keep making new accounts. They bid or buy-it-now on many items and hardly ever pay. Once they racked up an order of 40 or so coins and then never paid, costing me a lot of money in fees.
I think they are actually located in Ecuador, but have things sent to an address in the USA. I've reported them to Ebay customer support multiple times as problem buyers but nothing is being done.