The answer to, "What sign is most likely to cheat on me?" is, "Every sign." But before you panic - realize that there's no one sign that is more or less likely to cheat. It is about what makes each sign most willing to cheat.
Some signs seek excitement or want to see and experience what they do not have. Some are simply unhappy in what they perceive as a current negative situation, and feel lonely and neglected. Many potential cheaters have self-esteem issues and seek the person who makes him or her feel attractive. And, yes, a few are just chronically horny.
Aries fits into the excitement category. Rams feel with their ego, need attention, and thus fall into the self-esteem sector, too. Many flirtations are just emotional or about how much acceptance they can get. Although a fiery sign, many Aries actually run from forbidden attractions. They may consider infidelity, however, if their mate is unfaithful to them.
Taurus is known for loyalty, but like Aries, may cheat if the partner is unfaithful or is suspected of being so. A negative situation for Taurus is when they get little affection, touching, and attention. Cheating fulfills the sense of loneliness and neglect for this tender, loving sign.
With Gemini, lust isn't the motivator, it's intellectual cheating or intimate conversation more than sex. It's excitement, too, for this eternally restless sign. Also, when Gemini feels neglected and lonely, he or she reaches out for kindred spirits and shared interests to pass the time.
Cancer is another loyal sign, prone to personal guilt trips, so motivation to cheat isn't high. If they are involved, they often get entangled in love-slave/soppy romances. Moonchildren have self-esteem issues and are extra impressionable if they need "filling up" because they feel empty.
Fiery Leo craves excitement. Lions also fall into the self-esteem category because of the need to be the center of attention. A few are naturally horny, and thinking they are the world's greatest lovers, they set out to prove it. Leo is especially vulnerable to having a midlife crisis, drawn to charming individuals at least 20 years younger than they are because they want to feel youthful.
The Virgo is another potentially emotional cheater. In this light it's not a physical, but a mental affair. Needless to say, the sign of the Virgin is prone to heavy, personal guilt trips. The motivation to cheat might be that they have tried everything to make a relationship work, but they go to another out of frustration.
Libra likes to please. Natives of this sign do have strong principles, sound instincts, and take commitment seriously, so they aren't tops on the list of potential cheaters. However, this is a sign that finds it hard to say no, and is a potentially dangerous flirter. Librans need affection and attention. They may fall for the fantasy of finding infinite love, so most won't take cheating lightly.
Passionate, mysterious Scorpio gets a bad rap when it comes to their fidelity. Oozing sex appeal, they get accused whether they cheat or not. Scorpions fall into the need-for-excitement category, liking the intrigue of clandestine activities. They have strong physical appetites many can't keep under control. This is another sign that is out for revenge if a partner cheats.
Sagittarius is another sign that needs excitement. They wonder if there could be someone else or a grand, passionate adventure around the corner. An ultimate, starry-eyed romantic, they get in trouble when innocent flirting leads to something more. They panic when the passion gets heavy, which is one reason why they do try to do the right thing in a committed relationship.
Capricorn's nemesis is self-esteem when it comes to a lack of respect and feeling unloved. A few natives of the sign a find sex "naughty," and therefore exciting. Most Capricorns, however, discover that their worry takes the adventure out of it. This is another sign torn by guilty feelings and is very capable of controlling their "forbidden" passion.
Aquarius natives need to receive a lot of attention and to feel needed. Often, Aquarians are mates who are cheated on, because their partners need romance. Like Gemini, they get involved in intellectual cheating, or emotional affairs, instead of sexual flings or physically-based cheating.
Pisces' motivation is self-esteem. Like Leo, they could be lured into a midlife crisis situation. When they realize that life is short, they don't want to grow up, and may wonder, "Where's the magic?!" And like Scorpio, Fish are attracted to mystery and clandestine things. Ever the romantic, they can feel like a hot fling with someone new is fate.