A clock radio has a slider that selects the mode: “Alarm, Music, Off, On.” The “Off” position is the third position of four. I only just now realized that this is the result of conscious thought. Placing “Off” on either end makes it very easy to turn the radio off with a swipe of the hand, which is exactly what an alarm must not allow. The very meager amount of extra difficulty created by putting “Off” in one of the two interior positions probably makes the radio quite a bit more effective.
It’s possible everybody else in the world has already thought about this.
Quomodocumque 
Maybe not everybody has thought about this: my Sony alarm-clock has “off” at one end of the slider. I admit it is not the latest model. Maybe people at Sony thought about it AFTER they build my clock :-)
My alarm clock has an on-off button, but it’s much smaller than the snooze button — probably the same principle as work.
I’ve often thought in the past about figuring out a way to force myself to perform a nontrivial mental task (like solving a fairly simple math problem, maybe 3-coloring a graph) in order to turn off an alarm — the apotheosis of the “alarms should be hard to turn off” concept — but I have no idea how I’d implement something like that.