Some advertisers feel that paying entitles them to own the data completely - without interference by Google - and they're not reacting well to the change, with some threatening lawsuits. Others believe that Google retains ownership of the data, and they don't feel particularly hard done by. Then there are advertisers who think something in between those two things. They're not particularly ecstatic about what Google is doing, but they're not screaming about it - yet.
Of course, marketers should care about data ownership. The disturbance around Google's move raises questions connected with automation, privacy, and data storage. How this pans out could shape things for years to come.
So, where do you stand with regard to this? Losing access to information is never a good thing for marketers - it more comes down to what you personally believe you're paying for when you buy advertising. Do you purchase the data at the same time or not? Is this buying, or is it more akin to leasing office space? And if you just lease it, does that entitle you to use the data anyway? It's an interesting situation, and one well worth keeping an eye on.