What's the concern?

I find it interesting that some people have a knee jerk reaction/aversion to information sharing, or proceed to turn any mention of it into an over-complicated mess of a conversation.  I always seem to hear the same types of statements:

"We have privacy concerns"
"There is a lot of regulation that prohibits/impedes information sharing"
"That information is classified/sensitive/protected"
"We are not permitted to share information"

In my experience, when there is doubt or fear of the unknown, it's always easier for people to say no and then provide reasons that appear quite official and legitimate to support that position.  After all, no one ever got fired for not sharing information, right?  These individuals that choose this path, however, put their organizations at serious risk by needlessly limiting the organization's access to timely, valuable, high fidelity information necessary for incident response/security operations.

What's interesting to me is where this doubt/fear comes from.  As far as I can tell, it comes from a profound lack of knowledge regarding what is valuable from an information sharing perspective.  If long lists of sensitive internal assets were valuable from an information sharing perspective, I could totally understand the hestitation.  But, as it turns out, to our fortune, the most valuable information for incident response/security operations is publicly available Indicators of Compromise (IOCs), such as malicious domain names, malicious callback URL patterns, malicious email attachment names/MD5s, etc.!  It takes a skilled analyst and trusted circles of peer review to vet/filter the vast maze of information until it is boiled down to its most valuable essence.  But what is eventually shared is entirely focused on "footprints" that attackers leave in the sand after an intrusion, and contains no sensitive, private, or personal information about an organization.

So, I'm left asking, what exactly is the concern with sharing valuable, actionable, high fidelity IOCs within trusted peer information sharing groups?  Seems to me the concern is a fear of the unknown/lack of understanding what is valuable from an information sharing perspective.  I think it's about time that changed.