[WA]

For some data, this might be true. But, for example, where is my browsing history stored, which is undoubtedly collected by FB through their social sharing buttons even if I don't have an account? Or any other drive-by data that is collected through third-party apps, websites or whatever and send back to FB. It wouldn't make any sense to store my browsing history somewhere else than in a shadow profile.

[rock_hard]

No, it actually doesn’t make sense to store it in any kind of profile.

You are right that some fly by data might end up in a server log somewhere but those aren’t kept around for long...if they are kept at all at Facebook scales

Storing and computing data is very expensive and risky at FB scale so they will only keep around what they actually need for as long as they need it. Meaning that data gets send to the server, gets aggregated and then deleted.

An exception of course is content generated by users such as a newsfeed post, as is the nature of the product that content stays around until users delete it

[WA]

I have my doubts that storing compressed plaintext is expensive for a company that makes, what, 13 billion a year in profit or something like that? Their business is data. The more data they have, the more profit they can generate. The browsing history reveals a lot about humans. Storing it makes sense imho.