Just in case you wanted to buy a weapon from a friend
Bungie has just updated their blog in light of Destiny's impending launch, tying up loose ends as to what to expect, and their PAX Prime plans. Small things are being implemented like clan member increases to 100 players, but one major bit of information sticks out however, which is in regards to how the loot system works.
Every weapon you earn will be bind-on-pickup -- meaning, it will be bound to your account and only for you. Bungie's philosophy is that they want you to "earn" your items yourself, but you will be able to transfer them between characters under your account. Remember, servers go live "whenever it is September 9th somewhere in the world," immediately.
Bungie Weekly Update - 08/22/2014 [Bungie.com]