Differential privacy provides a lot less protection than you would think (or want to believe). A few months ago I saw a talk by E. Kornaropoulos, about his paper "Attacks on Encrypted Databases Beyond the Uniform Query Distribution"[0].
The main take-away from the talk - an in fact all the talks I saw on the same day - was that while DP is touted as a silver bullet and the new hotness, in reality it can not protect against the battery of information theoretical attacks advertisers have been aware of for couple of decades, and intelligence agencies must have been doing for a lot longer. Hiding information is really hard. Cross-correlating data across different sets, even if each set in itself contains nothing but weak proxies, remains a powerful deanonymisation technique.
After all, if you have huge pool of people and dozens or even hundreds of unique subgroups, the Venn-diagram-like intersection of just a handful will carve out a small and very specific population.