Keep your guest network separate
I was sitting in the parking lot and an open wifi showed up for me to connect to and I proceeded to connect. Immediately upon connecting I ran a quick scan with a free app that showed me all the devices connected to that network. I was surprised to find more than just wireless clients from guests, but also some of that business’s equipment as well. Guest networks are a great way to attract customers and give them added value if they have to wait for something at your place of business, but they should have a password, and should be completely separate from your business network.