That is not correct. It is still your data (that's why you need to grant a license to these companies to show your pictures even just back to you), and the third party doctrine is not settled law.
It has backing in precedent, but as ghayes cites above, the supreme court has given some strong signals that they would not agree with it today (e.g. in US v Jones). In addition, the incredibly important US v Warshak had the sixth circuit ruling that email in long term storage on a third party's server had just as much expectation of privacy for the owner as any personally held document. There are several companies now using that as a legal basis for requiring a warrant (which requires demonstrating probable cause) for account content requests (apparently outside of those coming from the FBI/NSA, unfortunately...), so it's likely this will come up before too long, either in Congress (I'd love to see the ECPA reformed but don't have high hopes) or in the Supreme Court, especially if another court of appeals rules differently.
I also have no idea why you cite Katz v US, as that's where the "reasonable expectation of privacy" test itself comes from, which runs directly counter to the later legal theory of the third party doctrine (in e.g. Smith v Maryland), which takes little account for reasonable expectations so long as you're handing off your communications to a third party.
My point that "you don't own it" is more from a security standpoint. ..which was pretty dumb to say. I can't verify that companies wont give my data to the feds and I can't trust them not to. It isn't my data to maintain anymore
It has backing in precedent, but as ghayes cites above, the supreme court has given some strong signals that they would not agree with it today (e.g. in US v Jones). In addition, the incredibly important US v Warshak had the sixth circuit ruling that email in long term storage on a third party's server had just as much expectation of privacy for the owner as any personally held document. There are several companies now using that as a legal basis for requiring a warrant (which requires demonstrating probable cause) for account content requests (apparently outside of those coming from the FBI/NSA, unfortunately...), so it's likely this will come up before too long, either in Congress (I'd love to see the ECPA reformed but don't have high hopes) or in the Supreme Court, especially if another court of appeals rules differently.
I also have no idea why you cite Katz v US, as that's where the "reasonable expectation of privacy" test itself comes from, which runs directly counter to the later legal theory of the third party doctrine (in e.g. Smith v Maryland), which takes little account for reasonable expectations so long as you're handing off your communications to a third party.