There are potential biases in the data set, but we don't think that they dramatically affect the results that we are seeing. Your mother probably receives spam phone calls and reminder texts from airlines just like I do.
A future project you guys should attack Basebands and see what kind of evil you can do because our govts are already doing it to track us
We used data collected from voluntary users' phone logs as our phone number data set. This means that if Joe called number X a few weeks ago and then decided to participate in our study, number X was in our database. We then used a couple techniques too see how well we could identify who number X belonged to.
We didn't put together actual profiles of users, though that is a possible next step. However, I think it is clear that putting together profiles of users is possible given how easy it is to identify who you are calling and receiving calls from.