Probably both -- not only is it more convenient for users to be able to swim between products, but having normalized and portable data is a godsend to anyone who needs to do data analysis. I'd imagine much more insight is possible when you can associate a user's activity on one platform to their activity on another. Imagine if your IP was shared between services; they'd know a lot more about you. On the surface, it sounds like a potential work around to GDPR.

So, bwillard, a member of the DTP project team, answered some questions I had along those lines in quite a lot of detail earlier today.

https://news.ycombinator.com/item?id=17577353

Probably both, and also in the interest of GDPR compliance (e.g. the "right to data portability").