Why this size?

[Delirium-Zer0]

The 3-inch CD single WAS the standard for CD singles in japan for a looonngg time. In 1999 however, just as companies were deciding that maybe they should be brought to the states & europe (back when singles were still sold regularly in the US... who remembers that? ), Sony killed the format worldwide, citing that it would be too expensive to make ALL cd players compatible with the 3" format. Most cd players & drives will let you play them... the only ones that don't (as far as I know offhand) are older standalone CD players (like home stereo sized ones that only play CDs and nothing else), many car stereos, CD changers, and the iMac cd drive.

Now that DVD players, CD drives, and portable MP3/CD players are the most common ways to listen to CDs (all of which are compatible with the 3" format), Sony are probably kicking themselves for killing off a format that would be saving record labels lots of money (seeing as how they're still very frequently only putting between 1 and 4 tracks on CD singles).