This photo by blmurch sums up the knowledge manager's dilemma: "Knowledge is addictive. The more you have, the more you want." And the more you have, the more you have to manage.
While this may lead to full employment for knowledge managers, it also points to the futility of the task we've set ourselves. We're trying to capture the ocean with a bucket.
So what is a more fruitful way of approaching this? Perhaps we should act as "knowledge purveyors" -- suppliers of essential provisions, rather than tinkers selling everything (including the kitchen sink). Or "knowledge facilitators" -- people who make things easier by helping colleagues find the knowledge they need. Or, "knowledge brokers" -- acting as intermediaries between the sources of the knowledge and the consumers of knowledge.
Perhaps it's time to revisit that KM Elevator Speech. As any lawyer will tell you, it's all in the definitions.