I don't necessarily like to see characters with addictions as their weaknesses. I mean, Snape and absinthe is obvious, right? But for me, it's a little too obvious. I think what turns me off the most about it is that while not everyone has addictive personalities, a lot of writers do, and I feel like a writer is projecting their own quirks onto a character when they give him or her substance addictions. It seems too...almost Mary Sue-ish, if you will.