It's a shame that more Americans don't vote but I'm not sure that compulsory voting enforced by fines would help matters. There are people here who don't register as voters because of the belief that voter registration records are used to determine who gets called for jury duty.
I find the idea of registering as a voter interesting, it's not done that way here. Voting isn't compulsory either but I don't think that our system would go over well in the US, despite the fact that our records aren't used for jury duty (because we have no juries in the way Americans have). It probably works only because Finland is such a small country with a heavily involved government but everyone is registered and when the time comes for elections they just go through the records and send letters to everyone who's eligible to vote. I'm sure there are people who avoid having up-to-date information about them in the records, though I've never heard of any and some people will forget to change the information when they move but if you want to have mail delivered to your home then you have to do it, the form for letting the post office know of your permanent change of address will also let the records keepers (the state church if you're a member or the magistrates, if you're not). I'm not sure if it would be possible to live an average type of life here without having the government know where you live (and once you let one department know they'll all know).
Because of another thread I've been thinking about how people without ID's vote, as you have to prove your identity when you vote. It's not particularly difficult to get an id here as you don't need a birth certificate (for anything), if you don't have an id the police will just interrogate you to make certain you are who you say you are (because they have records of all your past addresses, among other things) and though it's not cheap it's not that expensive either (though I only have a passport because of the expense, no other form of id) and I think that if you're that poor you're likely to be a client of social services already and they'll pay for it. And probably the majority of people have a drivers license, which isn't renewed here until you're something like 60. It's not really an official id (because you may be 18 in the picture and are now 58) but most places accept it, including polling stations.
ETA: I did some googling and apparently if you don't have an id you can get one from the police for free. I gather it's only good for voting. You have to pay for the photos yourself, which may cost 12 euros or less. A member of the parliament proposed that if people can't afford that they should get their photos taken at the police station for free. Minister of Justice replied that the police should be able to concentrate on police work and that it's best to leave photographing to photographers.