I can see how a reputation for lying would be a bad thing to have, but I can also see why a reputation for not being capable of lying would be a bad thing (mainly in social contexts). From one of my other comments:

For almost a year my best friend was dating a man without telling her ex-husband, and I was seeing her ex-husband every time I went to play with my godson, and I had to remember to lie about a whole bunch of random things like "what did you and my ex-wife do on Saturday?"

This was hard for me. There've been other times where I've slipped up and forgotten. Usually not in the context of friends explicitly telling me to lie about something, but in the context of Person X them telling me something which, to them, is obviously something that they want to conceal from Person Y because of conflicts it would cause. However, I don't model this–I model Person X and Person Y both as friends who I trust with details about my life, and assume that's commutative. I don't even think about it on a conscious level–it's not "I want to tell this person the truth about the thing this other person did because lying is complicated"–they just ask me a question and I answer it. I try to avoid having enemies because it makes things complicated, but that's not something I could force my friends to do, and it's not even something I would think was right to force them to do...I just don't get around to noticing potential conflicts.

Among certain groups of my friends, I've definitely earned the reputation for being a bit socially inept because of things like this.