LinkedIn has played a very poor strategy here. The value of the service should be in the network, which is quite defensible. Instead, they’ve made the value in the profiles, which is not defensible. Few people curate their network on LinkedIn because you can't see profiles unless you are closely connected, so you are incentivized to add as many people as possible, thus devaluing the entire network. Then they go and sell unlimited access to profiles to recruiters and sales people. Thus, when other services come around and scrape their data, which LinkedIn needs to make somewhat publicly available for SEO juice, it becomes an existential threat.

If you look at Facebook, there is some limited profile data publicly available, but they will go to the wall to prevent people from seeing how those people are connected. In addition, they started from a very walled-off position, so they didn't become reliant on SEO traffic.