Here is an old design:
So far all the logos have the exclamation point.
I wonder if it is part of the big changes that came with Yahoos new CEO, Marissa Mayer. She acquired Tumblr. She stir the waters by canceling telecommuting to work option for their workers. But my personal favorite - she changed maternity leave policy by giving the new moms twice longer paid maternity leave, 8 weeks off for dads, and cash bonus to parents. Go Marissa!