Question: I have a few buttons in my app whose alpha is currently set to zero. These buttons are completely non-responsive, but as soon as I increase their alpha, they begin to respond. Is this expected behavior?

Answer: 
I'm a little late to the game but you could always set the UIButton background color to clearcolor. This would keep them active. In my case, I am pulsating a button to give it a glowing effect but to do this, I must set it's background to clear, then add a UIIMageView as a subview and add the effect to the image, NOT the button. 

Hope this helps anyone else with this problem.
When the alpha is 0 they are unresponsive, as alpha = 0 is like hidden = YES and you can't click a hidden button.