I think the 'advantage of them, over a simple hole, is that the bottle and contents will tend to scatter the light around a bit, rather than just giving you a spot on the floor. The tubular shape of the bottle also compensated for the irregular shape of the roof.
Suppose it's one way of dealing with all those empty soda bottles.
Brazil's language is Portuguese; actually called "Brazilian Portuguese" because it has evolved some substantial differences (I have no idea what thay are) from the "European" Portuguese spoken in Portugual and some African countries. Brazil is the only Latin American country that isn't Spanish-speaking. Written Portuguese has a lot of similarities to Spanish, but the spoken language sounds quite different.
One of Brazil's gifts to the world is the golden-haired Xuxa (pronounced SHOO-sha), a former Playboy model who became a kids' TV hostess in 1983. Here she sports a *very* short skirt in the second anniversary edition of her ratings blockbuster "Xou da Xuxa": http://www.youtube.com/watch?v=R0xIt7S_dgs Needless to say, she was quite popular with the dads and big brothers.