text: You've just answered your own question by putting a comma after the exclamation mark in Yahoo!.\n\nIf you need to put a comma after the exclamation mark, why don't you need to put a full stop? If you think you don't need to add a full stop after Yahoo!, then would you ask a question with Yahoo! at the end of it without the question mark?\n\nNow, having a company name with a period at the end would be really confusing.