1) other people worry about voices inside their heads, and you worry that the voices inside your head are merely yours and not your characters'.
2) you eavesdrop for a 'greater good'.
3) nobody you meet in real life is as much fun as your imaginary friends.
4) people piss you off and you can't wait to get your revenge by putting them in your story (doing the literary version of a voodoo doll on them ).
5) you know you're getting ass-spread, but you sit and type anyway (guess this applies to online addicts too).
"To be conscious that you are ignorant is a great step to knowledge." ~ Benjamin Disraeli (1804 - 1881)