At its very essence, the term "world music" is a relic, a holdover from the days of colonialism, where the only music which had any real cultural significance was that which was developed in the West. It assumes some similarities between every tune that falls under its banner -- as if, because the music is unlike anything in the West, it automatically must have kinship with all other music developed in the non-West.
Clearly, the idea of any homogenous "world music" simply does not work. Every country has a different history; as such, a different culture, and therefore different music. Such differences are clearly illustrated by Unwired: Africa, a compilation from Amnesty International and the people who produce the Rough Guide series. The only common thread running through the album is that each track is a) African and b) acoustic. It should thus come as no surprise the style of music veers wildly from track to track. For instance, on "Valsa Azul", by Cape Verde's Simentra, one hears flamenco rhythms, while the next track, "Komssou", from Sudanese songstress Setona, is incredible tribal music.
You'll find those differences when you look at any two tracks on the album. Compare the bluesy "Jaman Moro" by Mali's Afel Bocoumhe, with the soft, gentle "Yamfa", a collaboration between Mali guitarists Toumani Diabate and Ballake Sissoko. Then compare either of those with the percussive "Hassaniya Song for Dancing", from Mauritanians Khalifa Ould Eide and Dimi Mint Abba. Each song is beautiful and distinct, proving with every note the ridiculousness of the "world music" tag.
Do yourself a favor: get cultured. But listen to Unwired: Africa without any ideas about world music, apart from the fact that to our culture and music would be "world music" to the rest of the world