> I find it odd that Facebook isn't scared of the same legal liability. Infact, they should be more scared.
You don't understand how partnerships work in this case. Facebook is paid to provide data according to a contract between the two companies. That's it. They have many, many such contracts to fulfill with many partners. These contracts don't say "we provide exactly the data you ask for, no more, no less" because that is a lot, lot more work and at the end of the day the contracts still get signed and FB still gets paid. A lot. Where do you see legal liability for FB so far? Their terms of service fully permit this data sharing, and the contracts are just between FB and partner companies.
Meanwhile, the partner companies use the shared data to produce value-added products which they provide to their customers under existing contracts and policies. They can't violate their customer's privacy or rights under any of the existing such policies, which are not identical to FB's. In fact, depending on the industry of the partner company, these policies can be extremely different. It is up to the partner company - not Facebook - to comply with the partner company's contracts/policies.
> I don't see any reason why Facebook would give away more information than they need to.
Facebook doesn't see any reason why they should waste time withholding more data than they need to. They still get paid the same amount, and the partner companies just filter out what they don't want. What's the point? There isn't even a big long-term concern here for Facebook, since extra social data isn't exactly very useful years later.
> They have the skill and resources to filter data themselves.
You say that, but every large technology company has to prioritize what they use engineering manpower for. Not everything a company can do or wants to do ends up getting done. For example, you might say "Facebook has the skill and resources to delete data from their CDN. I highly doubt they would throw away money on byte stored in Akamai" and yet they didn't do so for years and probably still don't. And that's a far easier problem with real measurable costs. Compare that to filtering the same enormous data set differently for each partner company when there's no compelling business reason to do so. The contracts are still going to be signed and Facebook will still get paid. Why should anyone care?
> I highly doubt that they would throw away personal and sensitive to other companies.
This is something FB is doing and have been doing for years. So your doubts are baseless.