It seems to vary on the store for how friendly they are. Yesterday, I traded in a laptop and, a relative traded in two. Today, I went to the same store with 3 laptops and got the stink eye from a manager when an employee confirmed I was there yesterday. The employee told me they can only accept 3 within 12 months, and hoped I would volunteer to leave. I didn't and asked about the two, which they accepted. While leaving Best Buy, the manager gave me a stink eye again. From what I've read, the policy actually is that you can only bring 1 per visit per day. Some stores are willing to accept more than that at a time. So, I think this manager was just on a power trip.
Really what it comes down to, this is still a good deal and maybe they just got a trade in rush the past couple days and were miffed. I'm not sure. What is hilarious is that this happened in a nicer part of town where people drive nice cars, whereas the other stores were much more friendly, but lower class.