Excellent thread. Ladder safety is huge in tree care. We use ladders a lot so I'm interested.
A 15-20 minute web search produced no definitive answers to the questions at hand, though this excerpt from a fire fighter site berates the method pictured in post #1:
"5. Footing the ladder: It amazes me that people are still getting taught to foot the ladder from the rear. The best place to be is in the front. You can see what is happening to the building, you can see what is happening to the firefighters climbing the ladder, you are in the perfect position for victim rescue (firefighter or civilian), and you can assist in taking the bounce out of the ladder. In addition you can keep an eye what is going on, and avoid falling debris."
Another fire fighter site showed 2 guys holding the ladder, one on each rail, footing it from the front. Nowhere did I find recommendations to hold it from behind as in post #1.
Most info recommended climbing by holding the rungs not the rails, but Kyle's reasoning re foul substances on the rungs at construction sites makes sense. And Sean's note that having the ladder footed by an adult standing on the lowest rung causes the weight rating of virtually every ladder to be exceeded is interesting, I hadn't thought of that.
It is surprising that despite the extremely widespread use of ladders there is no consensus on best usage.