I'm not sure about google because i signed for it a while ago but i'm sure that Yahoo didnt need your SS #
that sux.. wish i wasn't living in the U.S cuz people say u not suppost to show ur S.S number to anyone
it's fine as long as you aren't handing it out to everyone and their mother. if the program is trustworthy and the form is on https it is fine.
You just need to be sure the company is well known and reputable, and the page you enter the info in must be encrypted. I never put my SS anywhere if the page is not encrypted.