Looks pretty simple to me. Water always runs down and I would bet a large amount of money that the tree has a leak somewhere toward the top. Joint leak, metal rusted through, in a structure that big I wouldn't doubt a water leak could go unnoticed for a long time. Not sure how the branches are exactly connected to the tree but it would make sense if water ran down from above and ran out of a branch or just sat in a branch slowly decaying it. If that's all true what a pain in the A$$ to fix. I see it a lot where I live, rain and humidity combine adding poorly installed flashing and rot does follow. Flashing and sealing jobs always seem to be given to the lowest experienced person on the construction crew. Those nets could be there a while as in years and they are built well enough to last years. For that matter they are easy to fix so they could be there forever if need be. Just pretend you are in Monkey Jungle??? Tell the kids the nets keep the animals from dropping in on you??? Probably keep them occupied in they think they'll be attacked from above. LOL.
I saw some more pictures of the structure in question on Kevin Yee's column on Miceage . . . looks like they added some support struta for some of the 2x4s or whatever they are using (or maybe they were always there). Others parts of the structure seem to lack these.
The whole structure would have to stand-up to hurricane force wind, plus you've got those nets. I'm not sure what wind would do with them, but it might be enough to loosen the wood or just get the nets torn up. The nets themselves look to be made out of some sort of twine, not synthetic fiber. I am sure birds will start sitting on them, and pooping on guests below.
We can speculate about how permanent the nets look, (folks who build patios and decks could put up this contraption without much effort, maybe $5-7,000 worth of wood there, plus twenty hours labor, maybe $25,000 for the whole job?), but the nets don't FIX the problem of a 14-story structure with 5 lbs. pieces of it falling off. What if a wind blows a falling branch outside of the safety zone?
Meaning that it is almost certain that a major refurbishment will occur this next year. First they got to build a scaffolding, maybe takes them 2-4 weeks, then they've got to inspect for a couple weeks, then ??? who knows how much time to do the repair work. Though the nets make the area look safe, a big 100+ lbs branch could tear through the nets like a knife through butter, killing a couple of guests.
Even if there is a way for inspector to 'walk' along the branches, they wouldn't be able to fully see what is happening with all the 5 lbs branches. Disney would be liable if they didn't do the inspection and repair work after the accident as, obviously, the conditions that allowed the branch to fail affects the whole tree.
I doubt that anybody involved with building construction and safety, or a lawyer, would say, "Yeah . . . let's leave those nets up, that'll take care of the problem for the next five years. . . The netting they have is the cheapest way you could throw up something like that, poles, 2x4s between them, bolts to anchor them, some support struts . . . they didn't just sink the poles into the ground (which would make the wood rot faster), and usted a metal bracket, BUT this invovles less destruction to the queue and will be easier to fix when the nets come down. Anyway, the whole thing isn't themed at all, they could have add plastic camo-plants to the structure, or build better anchors for the posts, but they didn't. Even Alice's temporary railing in DL has some theming to it.
I know some people don't want to blame TDO . . . but regular paint jobs are important for even non-wood things like bridges, even cement can be eaten away by rain and metal corrodes. I suspect that there was a window, or a timeframe for recommended refurbishment for TOL and that TDO let the thing slide until the latest possible date, perhaps even making some new guesstimates about how long TOL could go without a refurb.