Right now there are about 12 Million Auctions on the US Site. There are about 300 Million Americans. So there is one Auction per 25 US Citizens.
Germany has about 80 Million Citizens and there are more than 5 Million Auctions on the german Ebay Site. So there is one Auction per 16 german Citizens. So in fact, ebay is already much bigger in Germany than in the US. Germany and the US are the 2 biggest Ebay Sites....wait for the other european and Asian Countries. There is still HUGE Growth possible.