Well me and Melyssa did it for Dexter's birthday (unfortunately it didn't trend), we're doing it for Greg, so we have to do it for Noodles! It wouldn't be fair not to.
I think this time the hashtag may trend because it's quite easy to use for other people, so they might use it for someone else which helps us. We can tweet it a ton for Greg K though so people who are Offspring fans will still know it's real purpose.