This is fairly standard practice. If you haven't already opted out, you may very well be opted in and sharing already. If you don't want that info shared then opt out. Simple. Keep in mind privacy is a somewhat subjective topic. Personally, I don't want to give these companies more than the very minimum to share. Either Google or watch NBC dateline for some basics on what permutations exist with various degress of personal data harvesting by corporations.
In late July I got an email from Verizon, my cell phone provider, asking me permission to allow them to share something they call my Customer Proprietary Network Information (CPNI) with other Verizon companies, affiliates, agents and parent company (Vodafone). According to this email, that includes things like the services I have, what I would call my usage information and data, etc. First, I thought that sort of thing is something that Verizon would already have been already sharing that info. Anyway, certainly I can see how this would benefit Verizon and all those companies, agents, etc, but I want to know what it does for me? What good is it, if anything, for me?