Parentheses are a tool of evil in writing. I realized in middle school that every place I used parentheses in a text was either an aside that needed to be placed somewhere else or removed, or something that could simply be incorporated properly into the sentence. Parentheses, like footnotes, promote the idea of a story as a word game, with little bits branching out that can be enjoyed on their own. This is Dave Eggers' idea of how to write a story and it is therefore evil. Writing is meant to be read and enjoyed for its own power; it is not the boring, long thing that you need to be distracted from occasionally. Parentheses should be avoided whenever possible.
Parentheses
From Everything Shii Knows, the only reliable source