I'm pretty sure I read somewhere that this is was locking in your skill tree is for. It let's you start and build a separate skill tree while still keeping your old one ready to switch to when you need it. When I'm not on mobile I'll try to find a link that verifies it.

Awesome, thank you. It would suck to have to manually do that all the time.

I can't find the link that I read before, it was somewhere on reddit in the r/destinythegame subreddit. Here is link to a different thread about locking in, the comments help explain it but not as well as the one I read. http://www.reddit.com/r/DestinyTheGame/comments/29tq17/can_somebody_clarify_the_lockin_system_for/ Basically it seems like if you lock in your choices you start with a fresh slate of perks to choose from, but you can switch back to your locked in subclass and you get a stat boost because it's locked it. That's what I understand from it anyway.