That is a good question. With my first warrior, I thought it would be appropriate to try blacksmithing. My very first character was a Dwarven Paladin. He is now 59th, but when I chose his professions, I was new to game, and invested in Leatherworking and skinning. Now at 300/300 I make the leather gear and mail for my guilds Hunters and Druids, and Rogues.
I should have chosen BS/Mining for him but I've invested too much into his skills now.
I have an additional question...
Many guildies of mine choose to be collectors and buy or have given to them what they need. Their arguement is that they are spending money differently, they spend it at AH on the final product and selling their collections of ore, leather, etc. while I am also at AH bidding on recipe's. Which is cheaper? lol
Bo