I might consider fdcservers. All other suggestions seem like are here just to promote their hosting :/
FDCServers is going to be a bad choice. For one, you don't want a European datacenter if the majority of your clients/users are in Japan. The routes from Europe to Japan are likely not going to be that fast. As I mentioned in the previous post though, the DMCA stuff is going to be your biggest problem. FDC absolutely honors DMCA requests, and specifically prohibits copyright infringement in their all of their datacenters, including the Netherlands. They are a US company based in Chicago, and follow the rules of the US. Keep looking!
Other customer's reviews of the hosting services. Same as any business, the hosting vendor should be able to provide good references.