It's still 'popular'. Heroin is made out of it, because it's more pure and gives a stronger 'kick'. Here's some information: http://en.wikipedia.org/wiki/Opium#Obsolescence

It lost its recreational popularity when advancements in the medical/chemistry field were taking place in the 19th and early 20th century, but it's still widely grown, because heroin has a large demand. Morphine is also derived from it.

Here's an interesting documentary: http://www.youtube.com/watch?v=IdYZj9vmfi0