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A. No, I don't. While I don't doubt for a minute that some talented people are writing fanfic, I believe there are good reasons why authors should stay away from it.
For one thing, there's the possibility that a similar story idea might show up in a fanfic piece, independent of your published story. It happens; I know an editor who received twelve submissions for a zombie anthology with the title "Working Stiffs." If you frequent fanfic sites, it's more difficult to deny accusations of plagiarism. If you simply don't go to them, no one can trace your IP number back to your computer.
There's also the time element. Writers are generally voracious readers, but there's only so much time you can afford to devote to reading. You're going to have to make choices, and no offense to fanfic writers, but I've got a huge stack of books on my MUST READ pile.
Energy is another thing in limited supply. It takes a lot of energy to get pissed off, a state of mind that can sap your creative energy at an alarming rate. I'd rather put my energy creating my own stories rather than getting exasperated about Drizzt/Elminster slash fiction.
If you write in a shared world, reading fanfic can lead to continuity problems. If you read fanfic that follows an alternate story path or simply fleshes out a little-detailed site or character, some of that info is going to get stored in your memory files and might accidently come out during the writing process. Years ago, I read an alternate-path story about one of the more intriguing characters in Marion Zimmer Bradley's Darkover setting, and today, I can't remember which details are "real" and which ones end up with Bobby Ewing waking up in the shower.