re: Explanation of Spieth's drop yesterday?

You can
1. Retee
2. Drop within 2 club lengths of where the ball rests
3. Drop in a direct line with the hole as far back as you want to.

Spieth took option 3. By going straight back he had to drop behind the equipment trailors. He was then entitled to the nearest point of relief from a temporary immovable obstruction (the trailors). Part of what took so long is to figure out what the "nearest point of relwif" was. Spieth wanted to drop on the right side of the trailors (which he ended up doing) because it gave him the best line, but he was near the middle so the rules officials had to determine if his nearest point of relief was to the left or right of the trailors.