LinkedIn is changing their business model to capture value from their users. As a user this means that it is providing less value to be on.
Specifically, without buying the second level of premium membership, you can no longer contact people who are 3rd level connections, regardless if you know them. As I am in a sales role, this is frustrating, especially the lack of disclosure due to the change in policy. All of the blocks that are put in place which prevent active usage of the network without a paying 50 a month are more than frustrating, especially for those who are premium members. More importantly, because non-sales pros are unlikely to get the premium services, standard users are less likely to be as well connected or use the service as much.
These problems are likely to slow the use of the network over time, and I expect that if the policies don't change I will need to use a different social network in 2 years as professionals grow frustrated and stop utilizing LinkedIn, especially those who are early in their careers--which makes the longterm story problematic.