i wouldn't think it'd be too much of a problem if the cameo is written quite obviously out of character, like kae's write-in as an evil pimp. it's not flattering, but as long as it's obviously all in good fun (and, as hazel pointed out, as long as you know the person well enough to know that good fun will be taken as good fun), it should be fine.
otoh, when you write someone more in character, that's where you start running into potential problems.
it's like with role-playing games (like dungeons and dragons). i was told by an experienced gamer that you should never create an RPG character too similar to yourself. if you do, you run the risk that when another character (who may say or do things that the person playing the character never would) criticizes your character or something (role-playing sessions often involve character dynamics, including arguments and such. some even get into romantic relationships between characters) you might take it personally.
cameos run the same risk.
for example, i have a head filled with random facts and trivia. i really enjoy being able to help people. i also have a somewhat overinflated and fragile ego (the two go neatly hand-in-hand).
put that all together, and you get someone who tends to jump in a little quickly with answers to random questions (i know random stuff, i love being helpful, and i also kind of like being able to demonstrate "see? i knew that!").
now, sometimes -- whether because of a jumbled memory, an incorrect source, an incorrect educated guess, or whatever else -- i get things wrong. of course, that's pretty rare...
so, anyway, wendy wrote me in to her story as a source who had called in a tip to clark. as it happened, it was a tip that didn't pan out. so, there it was, the line "sometimes hatman gets it wrong."
i knew the whole story was just meant in good fun and all, but it didn't stop a little niggling worry from the more fragile part of that overinflated ego from wondering if it had been a subtle jab at the way i tend to jump in and answer questions.
now, to be clear, this is just an example. it was just a niggling worry, nothing major. i'm not trying to complain or criticize or anything. what i'm trying to say is that a similar issue with a larger flaw could have caused problems.
the other thing is that when you write in-character cameos, you can end up focusing on the wrong aspect of the person you're writing.
take annie, for example. she hasn't said anything, but i've noticed that her cameos have all included a reference to alcohol. i've also noticed that on irc, there tend to be drunken annie jokes and references.
annie does get drunk from time to time, and she is willing to laugh about herself being drunk. she's also a happy drunk, which makes her really fun to hang out with and get emails from when she's drunk.
there's a lot more to her, though. she's a good responsible friend, a great editor, a talented writer, a reliable source of information on a variety of subjects, a great sounding board (especially on questions of moral grey areas), and she's fun to hang out with when sober (and she is sober more often than drunk).
seems to me that people have been losing sight of that with all the drunken annie references. it may be fun to joke about from time to time, but i'd think it'd be a bit much after a while.
so, basically, to sum up: be careful with how you write your cameos, especially if they're realistic.
Paul
