Aside from the privacy issues, I think this is the biggest cock-up of the whole thing: They managed to predict, with shocking accuracy, the fact that the girl was pregnant - yet they missed that she was a teenager living with her parents. This is why I worry about algorithms: We're extremely bad about identifying what's important information until we screw something like this up. In this case, the father called Target sheepishly. In other cases, he may have beaten his daughter or disowned her.
This touches on one of the biggest problems when using compute-driven data. I'm pretty sure the data could easily tell you her age and residential status... if you had thought of checking. Ultimately, the algorithms can only answer the questions you ask.
