I had 4 phone interviews over a two week period of time followed by a "skills exercise". I spoke first with their team lead who didn't seem to know basic product design terms and I spent most of that interview explaining them to him. In successive interviews I would hear those terms parroted back regarding new projects they were working on which made me think he was mining interview candidates for product direction. The "skills exercise" asked me to design a new feature to "increase daily active users" which they didn't plan to compensate for. A few days after I sent my exercise I was emailed a rejection that said they wished I would have "created something with more thought to mobile responsiveness" which was completely unrelated to the actual prompt they gave. Stop mining your interview candidates for free work and product direction. Pay for the work you ask for!