I think at this point, for most people, LinkedIn just serves as a repository for formatted resumes. Connections add a bit of value, as you can see where co-workers end up in the future.

The real problem is that for anyone with decent-sounding title, the amount of inbound spam is incredibly high. Endless outsourced development companies, recruiters, and random people wanting to connect for no discernible reason. Add to that a bunch of low-quality blogging, and I can't see how anyone can really enjoy spending time on the service.