Any effective knowledge management program must start with the end user at the center. Most KM implementations fail because they violate this principle. Instead, they define what the organization wants to know about itself, then devise a complex, centralized "canister" to dump knowledge into...and then tell employees to use it (occasionally, for added effect, they'll also mine emails and other data, generating neat graphs about how knowledge flows through the company). But, "What's in it for me?!?". If I, as an end user, use your system, how will I benefit? I'm sounding like a broken record, but blogs, wikis, and other simple social tools give the end user benefit...and once they have a reason to use the tool, the corporation benefits. That's the key to relevant successful KM implementations. PKN and Social Networks Change Knowledge Management (via Jack) says it well: "Personal knowledge networking and social networks give individual knowledge workers direct control over the enterprise's intellectual capital and enable a new "grass-roots" approach to knowledge management."
It sounds great, but I'm afraid it will largely not happen. I see similar things with the elearning market - so many viable alternatives to LMS offerings...and yet the cry of managers is "control, standardized look and feel (has that ever really helped learning?), enterprise-wide, etc.".