In the 30+ years since Sony introduced the Walkman personal cassette unit, the company has sold more than 200 million of the devices. Sony announced recently that they have permanently halted the sale of cassette Walkmans.

Related Fact: In another bittersweet moment for nostalgic computer lovers everywhere, Sony also announced this year that it will soon discontinue the sale of computer floppy disks.

[Source: Crunch Gear. Read Chris Higgins' latest post for more Walkman nostalgia. See previous Numbers of the Day here.]