This is really the exception in popular culture. Almost always in romance novels, movies and TV shows, the wife cheats (because the husband is ignoring her or she's bored) and it's lauded as exciting, naughty, liberating, whatever. (Is DESPERATE HOUSEWIVES still on?) Generally, in pop culture if the wife cheats, it's the husband's fault for not being attentive enough. If the husband cheats, it's still his fault for being weak or sleazy. Again, those hundreds of LIFETIME made-for-TV movies which air every day reinforce this.
None of the women I know say they agree with this or even approve of the message being sent. But one explained it's a little escapist fantasy, like the one for guys where a man walks in a bar and beats up five thugs bigger than he is.