We've seen literally thousands of comments and social media posts about the tangled web of former CIA Director David Petraeus' career-ending affair. Readers are talking about politics, the timing of Petraeus' announcement and possible long-term impact. But an especially popular theme that keeps coming up is fidelity and faithfulness, to which some readers say they can relate all too well.So we posted a survey on Facebook asking readers where that line of unfaithfulness begins. Is it fantasizing, flirting, communicating online, hugging, kissing or having sex? We received more than 2,000 answers to our unscientific poll, and as of 2:15 p.m. Wednesday, the majority of respondents said one may stray without ever making physical contact. About 47% of readers said unfaithfulness can begin when people are sending e-mails and texts without their partner's knowledge."I think it is the sneaking and lying that make it infidelity as much as the sex," explained commenter Jean Timmels. Another reader, Tess Gipson, said, "When the relationship has to be kept secret from your partner it is wrong. Otherwise you could bring the person in and sit them down in the living room and visit like a friend!"Drawing the line at sex was the second most popular choice, but it only got 20% overall."Kissing, per se, is meaningless," wrote Michael Wilson.Indeed, other forms of touch like kissing (13%) and hugging (less than 1%) were picked even less often. Some drew the line at flirtatious behavior (11%). We also heard from a few readers about fantasizing, which garnered the most comments but only 8% of the survey votes. Overall, readers seemed to place a lot of power in the mental aspect of love."It starts when you are thinking about it," said Belinda Lipscomb. "Because where your thoughts go, your actions will soon follow."Where do you think unfaithfulness begins? How do you feel about the Petraeus affair? Please share your thoughts in the comments area below.