Am I going to regret looting random chests and drawers?

Playing a mage in Dragon Age Origin, I notice that in the mage castle there are potions and lyrium dust everywhere, mostly in various chests and dressers, sparkling lootwise ala WOW. I have been just vacuuming this stuff up, but am I "stealing it"? Do I have like some alignment rating that is sinking into neutral evil, or can I just keep snorting all the lyrium dust I can find?

No, there is no alignment system that is affected by looting or stealing. There's just the relationship system that affects what your allies think of you based on the quests you do and decisions you make. Feel free to loot everything you see.