I have a healthy respect for lightning having my house hit and having it run down and arc out to the back yard less than 10' from me inside. My $0.02 having lived through that and engineer training and HAM operator training:
1) The arc was caused by the current running down the wet chimney and jumping over to the metal gutter when at the closest point. It then jumped out to the back yard, some random point about 5' off.
2) When it did this, it arc'd under the vinyl siding, on top of the tyvek wrap. Not sure why, I assume the Tyvek was more conductive than the vinyl. It did travel down the alum channels holding the vinyl, didn't damage them, but burned the hell out of the wall sheathing.
3) Faraday cage effect saved me from any damage. Insurance company forked out about $25k to do everything from rebuild most of my chimney (concussion shock someone mentioned caused that) to replace a bunch of electronics).
4) I don't sleep well in thunderstorms now.
That said, the lightning arc'd because of metal, at a height of approx 2.5' off the ground it arc'd over to ground. The bottom of the gutter was not connected to ground, so I can only assume that this height was where the potential was to a point where it could arc. For those doing the math, this is unfortunately about hammock height.
However, it jumped there because of the better conductor, metal, instead of following the chimney down. I would think that if you were hanging, it would simply follow the tree down. I don't have any metal in my hammock save a knife, though the Clark drip rings or the metal rings on the Whoopies might be electrically attractive. I would think it would follow the tree down, though, and just ground out there. At this point hammock would help you, as I don't believe it would have enough left nor a reason to discharge back up into the hammock from the ground. The one exception I could think of would be if the second tree is a better ground than the first, in which case the best course of action is prior planning, making sure you're good with whatever deity you prefer and life insurance is paid up, etc.
Assuming you do make it through the strike, I've not seen a tree hit by lightning where something didn't come off, if not most of the tree. That would suck, I think.
Final thought. When I was up in Ely in the North Amer Bear Center, they said bears climb trees instinctively during thunder storms. They've yet to have a bear killed by lightning. I think this speaks to the statistics of it, and the fact that most people "hit" by lighting are getting a ground surge. When my house was hit, only person who got any electricity was my daughter who was sleeping with an elec blanket that was shut off, it came back through the ground system of the house by induction, which I could explain how that happened but don't want to burn up bandwidth.