Can plain yogurt be a healthy substitute for mayo in a recipe like deviled eggs? Does plain yogurt have a taste?

I don't know about yogurt, but I substitute fat free ranch salad dressing, it's awesome.

 You can as far as consistency goes (especially with greek yogurt) but you may have to play with the flavors a bit. I usually use 1/2 light mayo and 1/2 FF plain yogurt if I really need the mayo-ie taste.