Yes, other countries may also have additional requirements.
However, there's nothing keeping foreign grids from registering a DMCA agent -- as Kitely has done.
And remember that Megaupload case? They have a registered DMCA agent on file with the US Copyright Office as well, even though they were based in Hong Kong: http://www.copyright.gov/onlin...
The US authorities *still* went after them for copyright infringement, however, claiming that Megaupload knew about infringing content and did nothing about it, and deliberately profited from infringing content.
It's a good idea to comply with the DMCA even if you're outside the US because:
* Americans like to sue people
* Americans create a lot of virtual content
* Many foreign grids have American users
* Oh, and Americans like to sue people
Remember that the DMCA isn't there for the protection of content creators. The DMCA is there to project owners of online communities (like blogs, social networks, and grids) from being constantly sued because of content uploaded by their users.
Nobody is going to force a grid to register a DMCA agent. Registration isn't an obligation -- it's an insurance policy.
One thing that patent trolls look for is places where users can post content, but the community owners HAVEN'T filed their DMCA agent registration. It's like having a big flashing bulls eye. The trolls threaten to sue you -- and, with fines up to $150,000 per offense, the victims are happy to pay a few thousand to make the troll go away rather than hire lawyers to defend themselves in court. The trolls specifically look for small organizations that don't have legal teams on standby, prepared just for this kind of thing.
Similarly, a grid can easily bring down a competitor by offering to underwrite the legal expenses of a creator whose content is on the other grid somewhere because, say, some .. umm... random person ... uploaded it.
If you have a registered agent on file, you just point the person to the filing, say "thank you for letting us know about this infringement" and take the stuff down. Without the DMCA, you either settle or hire an attorney.
By eliminating even one such case over the life of your grid, you'll have paid for the registration fee many, many, many times over.
Plus, it makes your grid looks like a solid corporate citizen. You're in compliance with DMCA. You have your registration on file. People can trust you.