Nice article Rand, thanks for sharing

Got a quick question about cross borders rules. Let's say I process
www.mysite.com with an US IPSP from an US company and now I also want to process for the same stuff with an EU IPSP from and EU company.
Do I need to register a completly different url for that or are subdomains ok?
Is
www.mysite.eu acceptable? (I guess yes)
Is eu.mysite.com acceptable?