As far as friends and lovers go, I have to admit I tend to experience most of my relationships as power games. I don't know if this is actually common, but I suspect it should be. I readily perceive the balance of power, I ask myself how far I can control and dictate behavior in others, and I'm overly sensitive to their attempts to control me. I use many techniques to secure power. Emotional people who are strong-willed are terribly sensitive to histrionics, for instance, whereas emotional people who are ultimately weak are better stunned by a display of swagger and cruelty that creates awe and submissiveness in them. I really "feed" off people's emotions and enjoy gaining their trust and devotion. I particularly enjoy leading them to make choices that run against their principles... in their efforts to reconcile their beliefs with their actions, they convince themselves that their love of me is so strong and noble that they courageously have shattered their principles to be "true to their hearts." (Ridiculous, isn't it?) Needless to say they then perceive me as "exciting" and "unique," and attach themselves even more to me, which leads to even worse acts of self-humiliation and submissiveness.
Furthermore, I really cannot maintain a monogamous loving relationship. I've tried... with wonderful people that were smart, engaging, funny, and devoted. Nowadays, it's a matter of weeks till I'm utterly bored and start fucking other people, including their best friends. My sexuality is as flexible as the rest of my personality, so I can be straight, gay, aggressive, romantic, a fucked-up jerk or an innocent dork. I am not extremely good-looking (though I keep healthy and in shape) but I've had several simultaneous parallel relationships. Some of my partners even knew about my other affairs and were totally fine with it, even when I asked them "Do you realize I'm just using you till I'm bored?" I have thus developed a moderate contempt of romantic relationships and their special nature, and tend to view them as a basic need (like food, sleep and sex) that people are willing to go to any lengths to secure.
Finally, as far as hiding goes, I have the best mask of all: nervousness. Nobody (really, nobody) thinks you're a bad or "dangerous" person when you're nervous. Bite your lips or fingernails, appear shy and clumsy, look innocent and act lost and out-of-place, and the worst you're gonna be perceived as is "incompetent," maybe a "loser." Furthermore, a person who seems incapable of controlling their anxiety is almost always trusted. No one believes that someone lacking the ability to pull themselves together can actually scheme and manipulate situations, or even be mildly strategic.