In practice very little. The FCC tends to focus on long-lived stationary stations ("pirate" radio) with their few enforcement actions. That said it's important to remember that radio transmissions can easily be tracked to their source (doubly so with drones) and you should plan for that eventuality.

My sense is that at most you will be yelled at by HAMs - unless you are actually disrupting emergency communications. Ensuring radios can be used in emergencies is why licensing exists at all and people take ensuring it can be used for that pretty seriously (for good reason).