LinkedIn is one of the top sites for dark UX patterns. It is 100% purposeful, just like Pinterest, and designed to increase the all important "engagement" metric.
IIRC, they were about some technical topics, similar to what you'd expect to see in a blog. Why they close to use Linkedin I don't know, but apparently it does happen.
Millions of new posts, job searches, private messages and other activities take place everyday. They do have plenty of spam and a terrible UX but that doesn't mean the site and community is anywhere near empty or useless.
Things such as who else they work with, their exact position in their company, where they have worked in the past.
All the social features bolted on are useless to me.