I think rather than specific concerns, it's for people who have a reluctance in principle to let large private corporations (or anyone else for that matter) have any more information about them than absolutely necessary.
I'm not really a tinfoil-hatter (I use Chrome and don't lose any sleep over what Google might be doing with the info they're getting from me), but I do think it's a valid point of view and I can see where they're coming from.