It's a no-brainer decision from a security point of view.

The only exception that I would consider would be allowing for remote virtual desktop or virtual app access. Even that has risks that needs to be considered.

Remember that with BYO, unless you're providing stipends for employees to buy equipment with string attached, you're not dealing with just your employee -- you're potentially thinking about the employee's extended circle of associates. The employee's kid, parent, drunk roommate, etc all have access.