Ever since I upgraded from Snow Leopard to Mountain Lion, my MacBook Air doesn't wake from sleep when I touch my trackpad. I have to physically click it in order for it to wake up, which can be quite annoying sometimes since I'd rather not have to press the physical button underneath the trackpad (and it's easier to just tap it when your finger or move your finger on it, as if you're moving the cursor around on the screen).
Does anyone know why it doesn't work the way it did on Snow Leopard?
In Mac OS X 10.7, aka Lion, Apple removed the ability to wake the Mac by moving the mouse. This stopped knocks to the table and pets moving the mouse accidentally from waking the Mac.
By clicking or pressing a key, you are being more deliberate about your intention to wake your Mac. Ideally it should help avoid waking your Mac accidentally and save a little power.
As ever, this improvement benefits some users more than others.
I don't know if this is a setting which has changed, but my first thing to try with any hardware or sleep issues like this is to reset the System Management Controller (SMC). I find this usually fixes all sorts of sleep, boot and external monitor issues.
On my 2011 13" MBP these happen at least once every couple of months.
This has always been the behavior for me. Sometimes even clicking doesn't do it, and I have to press the spacebar. Note that tapping the trackpad is generally not considered a click in this context. Even if the screensaver is running, tapping the trackpad just undims the screen, without closing the screensaver.
