There are many organisations where knowledge takes a very indirect route from knowledge provider to knowledge user. Instead of peer to peer knowledge sharing, knowledge has to go "over the hedge" from one department to another, transferred at management level.
In a Hedgehopper company, if someone at an operational level has a pressing knowledge need, they ask their manager, who asks their manager, until the request reaches someone senior enough to travel. At the next global managers meeting (often called a global network, or even a knowledge sharing network), they can raise this question. Maybe someone knows about someone in their own organisation silo who can help, so they pass the question down the levels until it finds someone at operational level with an answer. In the better hedgehoppers, the asker and the answerer are put in touch with each other.
In the worst hedgehoppers, the answer also travels up the heirarchy to the travelling experts - then back down again on the other side.
Do you know the term "Chinese whispers"? This is Chinese Whispers with a vengeance. Not only is the transfer of knowledge delayed until the hedgehoppers meet, the knowledge is filtered as it travels up and down heirarchical levels, until by the time the answer arrives, it may be too late, completely garbled, and largely irrelevant.
What's the alternative to hedgehopper KM?
The alternative is to allow peers all over the organisation to communicate directly, without having to go through managers. You set up the communities of pracice to allow peer networking, you encourage and promote peer assists, and you empower people to seek answers wherever they may be found.
Partly the hedgehopper concept comes from applying the concept of T shaped management, without realising that anyone in the organisation can operate in a T-shaped space - looking both vertically at the heirarchy, and horizontally at their peer group.