This has happened to me on several occasions at uncontrolled airports. The 1st time I missed a mid-air by approx. 20 ft. (I was solo with all of approx. 25 TT at the time, and as someone said earlier, I was completely focused on the runway, not the airspace around it). I failed to remember that people can be off freq. in such an environment, and that there are even some guys who still fly without a radio (nevermind it's the 21st century and handhelds are relatively cheap vs. losing your life).

The thing is, you don't have to be turning to final to have it happen either. I've seen guys fly straight into base while I'm on downwind getting ready to turn base (instead of entering on the 45 to downwind) without making any radio call, and I've also been on a left base-to-final only to see someone else on a right base-to-final, coming straight at me. It's amazing, but some people still fly without radios, much less not being on freq.

If it's uncontrolled, my head is on a swivel no matter where in the pattern I'm located, and I follow entry and pattern procedures to the letter. It's why they were established in the first place.

.02