Simply put, you cannot RP an evil character with most folks. They do not wish to lost their money, their pride, or their life. Playing a good character is easy, because if you don't wish to RP with someone who is trying to be evil, you can just ignore them. You are still 'good'. Bad RP, but true.
However, if you are on the flip side, and try to RP an evil char and get ignored, guess what? You aren't evil. By being ignored, your character is reduced to nothing. It also does not help with the good always wins attitude. Playing an evil/bad character is a two sided thing. If it is only on your side, you are considered a spammer by those who are playing 'good' characters.
Now, I have a character I consider bad (not evil). He is a thief, and will steal from his own grandmother. He will lie and smile in your face in the nicest manner while cutting your purse. He is not a killer, however. In character description, I gave his looks and apparent attitude. I then went on to state in all CAPs "THE FOLLOWING IS OUT OF CHARACTER. YOUR CHARACTER WILL NOT KNOW THIS" followed by my stating that he is a very good thief and has never yet been caught. I explained exactly how I wished to RP this character, and how to deal with him.
One of the first people I met was someone I considered a good RPer, and had never met with this character before. The first thing he did was eye me warily. The second was to tell his comrade to keep an eye on me, that I could not be trusted. I asked ooc why he would say that. My answer was that he had been around for over a thousand years and saw me a few times before, noticing things vanishing after I left. My session of RP ended right there.
In conclusion, you are only as evil as others let you be. Good characters can rely on game mechanics, bad characters have to rely on other people.