A Co-worker pointed this out to me:
The general belief is that it was chosen because the CD designers wanted to have a format that could hold Beethoven's ninth symphony. They were trying to figure out what dimensions to use, and the length of certain performances settled it.
There are several different versions of the story. Some say a Polygram (then part of Philips) artist named Herbert von Karajan wanted his favorite piece to fit on one disc. Another claims the wife of the Sony chairman wanted it to hold her favorite symphony. An interview in the July 1992 issue of _CD-ROM Professional_ reports a Mr. Oga at Sony made the defining request. (This is almost certainly Norio Ohga, who became President and COO of Sony in 1982 and has been a high-level executive ever since.)
The "urban legends" web site has some interesting articles for anyone wishing to puruse the matter further. The relationship of Beethoven's ninth to the length is noted "believed true" in the alt.folklore.urban FAQ listing, but no particular variant is endorsed.
Searching the net will reveal any number of "very reliable sources" with sundry variations on the theme.
He also pointed me to: http://www.chipchapin.com/CDMedia/cdrom3.php3, which is a great primer on CD audio, including why CD data sectors are 2048 bytes while CD audio sectors are 2352 bytes.