The Two Rivers people don't think that they have Darkfriends among them, and don't really get stirred up by the Whitecloaks' Dragon's Fangs and all that jazz.
As to Ogier, Robert Jordan has said that Ogier could become Darkfriends, but not whether there were any or not.
I'd think there aren't any Darkfriends among the Two Rivers folk, simply for the impracticality of it. The Two Rivers is so isolated from the outside world, there would be little to no chance of networking with other Darkfriends. And it's harder to do something evil if there's no one to give you an alibi or corroborate your story. A single person doing evil stuff in a place as small as Emond's Field would be caught pretty quickly, I'd think. Plus, the benefit to TDO would be low to nil having Darkfriends in the Two Rivers. It's easier to cause chaos in towns and cities that have more trade, more people, and more influence.
@ Rhed al'Tere: Yes, I agree - and I think the networking aspect is essential - take any belief you like, but you need a community however small to sustain it.
I think it's possible that there'd be a darkfriend or two somewhere in the Two Rivers, if not necessarily in Emmond's Field. Maybe Taren Ferry, as they're closer to the outside world.