LinkedIn is arriving very late to the social applications party. Comparing your Amazon reading list with those of your network, sharing your blog posts and travel plans with your network, or using online workspaces -- these things are not novel, and you are probably already doing the same thing elsewhere. Are you going to limit yourself to the LinkedIn world to do them? Perhaps LinkedIn would be better off providing an API into their network or networks for use by external application developers?

Furthermore, though LinkedIn , the platform is not publically available. The company makes this statement:

The LinkedIn application platform is not publicly available for all developers. We evaluate requests to develop for the LinkedIn platform from partners who have clearly compelling value to our users and who can rigorously follow our privacy policies. We are looking for applications that provide clear business utility to LinkedIn users. LinkedIn is not a place for sheep throwing.

If I have an application with a clearly compelling value I don't need the approval of LinkedIn; I can just build the application either by myself or for a different platform. This is not the way to attract developers. And developers are needed to create the applications that will attract people to LinkedIn. Not rehashes of existing products.

After all, as my recent experience with the iPhone app store shows, it appears that there are many excellent productivity tools that don't involve sheep throwing at all.