re: "Now, if that was all they had? They might find a way up."
An excellent point. I'm not particularly scared of heights, and I do have some rock climbing gear from when I was younger and more adventurous. But I've been 25 feet up in a skinny tree before, and when even a gentle wind gets that thing swaying, it's scarier than you'd think.
In the task I'm referring to, I was trying to take down a tall tree that was between two houses. I figured I'd top it first, then deal with the base. But when you're up that high, you need to tie yourself to the tree while leaving both hands available for the chainsaw. I got it partway sawed, then started having horrible visions of what would happen if the top snapped and came down on me or, even worse, what would happen if one of my safety lines fell to earth with the top half of the tree (and pulled me with it) while the second kept me firmly affixed to the trunk at 25 feet!
Yep. I could've had my own Darwin award!
I wound up sawing only PARTWAY through the tree trunk, then used my pickup and a long, strong rope to snap the tree in two. That worked fine and wasn't anywhere near as dangerous as what I'd been doing.

Gold is $1,581/oz today. When it hits $2,000, it will be up 26.5%. Let's see how long that takes. - De 3/11/2013 - ANSWER: 7 Years, 5 Months