Topics in Yammer... errrrr... Viva Engage. I've been in so many hot debates & strategic conversations about them over the years! Bottom line - using hash tags has traditionally been the "manual" method to try to accomplish what algorithms are trying to do automagically... In other words - surface the content most relevant to me.
Historically, the challenge is almost too obvious: the desired outcomes only occur when several conditions are met:
1) I subscribe to the items I want, and
2) Authors correctly tag the items that exactly match my subscriptions
The gaps are significant... Not the least of which is the variations in taxonomy. If I subscribe to https://www.linkedin.com/feed/hashtag/?keywords=projectmanagementProjectManagement but they tag the content with https://www.linkedin.com/feed/hashtag/?keywords=projectmanagersProjectManagers ... well, we both lose.
The functionality we need to help make this functionality valuable is Administrative Control. The ability to edit tags with typos, the ability to flag certain tags as synonyms (like #ProjectManagement = #Project-Management), etc. Even then, success is tied to the amount of overhead the administrators are willing to take on.