Normally companies retire products because they are lightly used or have fallen far behind competition. Google kills stuff on whims. Google Reader, url shortner, code search, Picasa - all these are terrible examples of things that got shutdown.

All these has real consequences. Other day I was looking to buy a movie and it was available on Amazon as well as YouTube, I went to Amazon because YouTube feels much more likely to shutdown it’s movie business on a whim while Amazon will likely fight out to last moment. Same goes for buying music.