Milton Glaser, a veteran graphic designer responsible for the iconic "I heart NY" design of the late 1970s, says the exclamation mark is meant to "generate a sense of enthusiasm and excitement.

Yahoo!s Now Removing The ® From Their Logo. Is The Exclamation Mark Next? Alexia Tsotsis. 12:28 AM PDT · September 18, 2012. File in “Silicon Valley Things That Are Amazing/Ridiculous”*: ...

However, while the updated logo is intended to reflect a new corporate personality, Yahoo made clear it would retain the familiar exclamation point, purple complexion, and trademark yodel that ...