To reproduce:
1. Create a new script
2. Add these lines to the script:
"
void OnGUI() {
if (GUI.Button (new Rect (0, 0, 300, 100), "Press")) {
Debug.Log("logging");
}
}
"
3. Attach the script to the main camera & build for WP8
4. Open the solution in VS and deploy to an emulator (I'm using WVGA 512MB)
5. Note the output - it is filled with "logging" even though the button was never pressed

Does not happen in 4.3.4f1