Sorry folks but I fail to see the point unless solely as a novelty!
I am aware that there are some cultures that live in trees out of necessity, as defence against flooding, predatory animals, etc, and at least one forest people who have taken this to the level of status symbol with regard to the comparative height of the dwellings.
In the tropics, there are a variety of venomous snakes which live in the canopy and hunt in trees and many insects which might take exception to your occupation of their protectorate.
With regard to bears, an American I used to work with once said of grizzlies, "There's no use in climbing a tree. That just means you're going to die up a tree!"
We have no dangerous predators in the UK and only the adder is actually venomous, which won't bother you if you don't bother it. If you fear biting insects and ticks then you might want to reconsider going into the great outdoors at all, as midges, mozzies, clegs and various other Munchers are no respectors of height. If flooding is an issue then move to a sensible location, as it might take Search and Rescue a while to get round to you.
I've spent as many nights as I wish to benighted on mountain ledges, cracks and chimneys, or in what we used to call a Tiger's Web. I can think of a few which were memorable, usually due to misery, but none which were comfortable, gave a decent nights rest or bore the luxury of a fire.
Give me cave, overhang, doss, howff, woodland, mountain, coastline, loch or riverside any day and I'll be a contented man beside my fire.
The only explanation I can think of for anyone wanting to sleep up a tree is that they've never been cold, wet and miserable.
