Plancast is a social networking service many expected to become a fixture for those who like to give “friends” opportunities to be where they’ll be and do what they do.

The service has already floundered and is now dying on the vine.

This link leads to a very good analysis of its failure by its CEO, Mark Hendrickson. His timely comments perfectly reflect why I (a very early adopter) couldn’t use the service on a regular basis. As far as I’m aware of this analysis is a first for the social sector.

Also interesting are the comments of people who (as I did) liked/loved the service and honestly tried to use it as much as possible but for various reasons couldn’t. Scoble himself appears to have been  the first to comment.

The article: The Uphill Battle Of Social Event Sharing: A Post-Mortem for Plancast

Why am I sharing this? If nothing else, it provides tangible evidence that “great” ideas must have a viable model and a willing market that will achieve the critical mass necessary for success. Just my 2¢.