Well, to be pedantic, not all of the countries mentioned
have compulsary voting. Belgium for instance require you
to show up at the voting station, but you don't actually
have to cast a legal vote. Still, it's a short list, most countries
don't have mandatory voting, and it's certainly not uniformly
accepted to be a good thing.
The article also links to http://www.int-idea.se/vt/analysis/Compulsory_Voting.cfm
which points out some of the drawbacks of mandatory voting
(random voting for instance).