"Angels fly because they take themselves lightly." — G. Chesterton Flirting adds spice to life and supports positive attitudes toward other people.
It may involve flattery, but it is a subtle and enjoyable flattery that is closer to praise than to a lie.
In the following description, a married woman having an affair with a married man illustrates the shift from the playful nature of flirting to the more profound nature of a committed romantic relationship: "We flirted with and [sought] each other constantly, until one day we realized we were not just playing anymore.
This site, whose motto is "Married Not Dead," offers the following guide to flirting: Flirting encompasses seemingly contradictory notions: Honesty, with an element of innocence, as well as a mild level of deception (expressed through flattery); caring for others—by listening to and showing interest in them—while not taking them too seriously; being confident and feeling good about yourself, while not attaching too much importance to yourself; and intelligence, flavored by an emotional tone.
All these characteristics are evident in online affairs.
Flirting is like an inactive volcano that can become active any moment.
In online affairs, crossing the line between innocent flirting and overt sexual interaction, and hence activating the sexual volcano, is greatly facilitated.