Never, no more than I register for any other country's copyrights (Finland does not have a registration procedure).

http://www.bjorklid.net/ http://www.huumakuva.net/

You raise a good point, Kalle. The US is the only country I have found in my research that provides any tangible benefit to registering your images. It also appears to be the only country that provides a mechanism and a central body for maintain a registry of images (or any other copyrighted work).

In the US, registered images reap bigger rewards for the copyright owner in the event infringement takes place. In most other countries, the remedies available to the copyright owner are the same whether an image is registered or not. The US copyright system is more complicated, however it affords copyright holders significant benefits in terms of remedies, and tarnishes the reputation of the offender who then has a Federal conviction record if their case goes to trial and they lose.

Is the US copyright system a better deterrent? I can't say. I think copyright infringement is just as rampant in the US as it is in many other countries.