"The most obvious application of the mere-exposure effect is in advertising, but research on its effectiveness at enhancing consumer attitudes toward particular companies and products has been mixed."

"A subsequent review of the research concluded that exposure leads to ambivalence because it brings about a large number of associations, which tend to be both favorable and unfavorable."

This would make sense, since it's the unfamiliarity itself that elicits a negative response. Once that unfamiliarity is gone, you'd react normally (positive or negative). We're all familiar with Facebook, Google, Ford, Tide, dogs, hamsters, veal, brussels sprouts... But that doesn't mean that we necessarily have a positive view of them.

So the "Mere Exposure Effect" remains unproven for positive response in an advertising context.