Radio commands are far more effective when used in moderation and with a team that is listening.

The radio commands should not be made more than twice at any given point in time. The reasons are simple. First if even 2-3 people notice a problem in the base and they all use radio commands to call for help. they will clear most players text box and fill it with the same message. This runs the risk of removing an important instructions for other players that my be trying to do things in a different part of the map. Second some players won't respond to a radio command if they have to see it 6.02214199 × 10^23. It is usually more effective to just type the name of the biulding followed by some of these "!!!"

Do not bother to make a radio message calling your team to save a building if you yourself are not going to respond. No matter how cool your Havoc/sakura is its going to feel bad when you lose your hand/barracks. If you tell your team you saved the building but lost your unit they usually will reimburse you for your loss.

To summarize take the radio commands seriously. They are like any vaccine great when used on people but over use them and they won't protect your base like they should.