The final batch was produced in Japan in April, and no more will be produced as soon as the current run is sold out. Just over 200 million cassette Walkman players have been sold over the years since being first introduced in 1979.[...]
The Walkman is widely credited with pioneering the concept of personal, portable audio beyond the radio. It helped spur on the cassette as a popular format and also maintained interest in albums. Interest only began to fade in the 1990s when the Discman took over, and saw a more definite end when the iPod was in sight.
Link via reddit | Photo by Flickr user zer(o_0)ne used under Creative Commons license
Both (iPod and Walkman) were game changers in their category though, largely making them a lifestyle device, mostly in marketing and good engineering.
The difference is, Sony largely started the category, while Apple joined an existing category of somewhat geeky technical devices, and engineered it into a lifestyle device anybody used.
I showed it to my son and he laughed at the brick like size of it