Bringing your own devices to work
The biggest problem for the IT departments at small or large companies is when employees bring their own devices to work. There is no necessity for employees to bring their own devices to the work place. The problems they can cause to your network (both purposefully and accidentally) can be catastrphoic for your business.
Companies should make sure their network is secure from outside devices, as well as having a policy for an employee's personal device. It only takes one device, like a smartphone, to connect to your network and disrupt the entire server, causing the network to malfunction and/or leackage of private information, such as bank accounts.