Well, sometimes the announcing is enough, if it gives others the incentive to introduce themselves. (I find this works better for monosexuals, though... I frequently bewilder people when I talk about both my husband and my ex-girlfriend.)

That is an effective signalling strategy, but unfortunately would be ineffective in certain situations, including my own, where the matter of concern often involves trying to determine the answer in the absence of stereotypical indicators or a relationship history of sufficient length (e.g. one or zero) to draw conclusions.