What is Your real feelings about it? Somehow do you feel Your cheating by doing it? Just remember "EX", there was a reason for that person to become an "EX". Best thing is to move on and keep the good memories and don't start new bad memories by digging up the past?
You want to check on her or talk to her? Is she doing OK without you? Is she doing better?
Is calling your ex on the phone cheating?
Is writing your ex a letter cheating?
And what about My Space? And Twitter?
Of course, an excessive interest in and expression about your ex could lead your current partner to exit and become another ex.
It depends purely on your motive. Curiosity? Discussing it with your current spouse beforehand? Keeping it a secret from your current love because deep down you are hoping to get back with your ex? If I were your current spouse and you did it without explaining to me why you were interested, I'd call it cheating. Interest in another (on the sly) will make your current spouse feel as if you've cheated. Secrets like that can be destructive.
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Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them