Responding to an email like that has basically no possible benefits for the person running the balloon tracking website, but it does introduce the possibility of some fool paying their lawyer to add you as a respondent in a lawsuit. Costing you many thousands of dollars at minimum in legal fees and travel even if you get the court to remove you from the case. Never respond to something like that unless your lawyer, whom you pay has instructed you to.

A person like that sending inquiries to website/API operators demanding data, ignore it. Always. Continue to ignore it until a process server actually shows up on your doorstep and serves you, in which case you know they're at least moderately serious, and then you need to engage your own counsel to deal with it.