For me it's something I'm mulling over. On one hand, I wanted to be horde when I first started- but all my r/l frinds were Alliance. This would give me a main which could, in turn, fund my horde alt so that I could level him in relative comfort to 80.
On the other hand, apart from Ellieann (my rogue), all of my characters rely on each other for their professions. Steelbelly has enchanting and recently switched to inscription. Marlene is the herbalist and alchemist- so Steel relies on her for his herbs, Nexnecis relies on her for jewel transmutes, and she makes everyone's potions and elixirs. Malesar is a skinner and leatherworker- so he makes gear for himself and for Steelbelly- and leg kits for everyone that can use them. Nexnecis is my miner and jewelcrafter, so he gets to make jewels for everyone... well, once he gets all of the recipes.
Ellieann is a miner and engineer, so she'd be able to make the switch without adversely affecting anyone else. However, I've grown fond of my Gnome rogue, and she also promised Steelbelly she'd make him a motorcycle, so he'd be hurt if she left before she kept her word. Besides, I don't know if I want to spend $30 just to switch her to a "maybe I'll play her as horde" character- and then find out I don't like it on that side as much.
