I’m a Magento Developer and I experienced the same thing when interviewing with Insteon. I don’t how often this happens, but there’s little one can do about it. One rule of thumb is if they start asking you in-depth information while not showing interest in you, then there’s something nefarious going on. There’s nothing illegal about these practices; it’s all gain for the company. While the candidate is wasting his/hers time going throught he whole process, at the same time “giving the store away”.