I'd say the use for personal identification is cross-platform linking of users. I.e., this user on Google Search and this user on Google Maps are the same person. I agree that this is a competitive advantage, because, in the same vein, it gives the platform owners more data. Technically, anonymized cross-platform-linked data is conceivable.

I think if the legislation ball ever gets rolling two things we're likely to see, because they're low-hanging fruit, are the end of mass tracking on the internet and a meaningful shift in who controls the data gathered.

I can imagine a platform akin to internet banking where you manage your data and its usage.

Something I'd love to see is a "publication" of big-data algorithms. A private entity designs the algorithm for profit and leases it and you run it in your (trusted) environment, owning both the input and output. Nothing leaks.