When you click "share with followers" it adds the hub to the feeds of your followers on HubPages. This is a separate action from tweeting a hub or using other outside services.
In a recent discussion on the forums (November 2011), a hubber raised the issue of hubbers who use this feature a lot. Some people opt to unfollow hubbers who "overshare."
Based on what I've seen in my own feed, when hubbers do this too often, it clutters the feed. The consensus seems to be it's okay to share a substantially revised hub -- just use this feature sparingly.
One of the best uses of this feature is to share a deserving hub by another hubber with your followers.