@alisha, @MikeMason-- I don't think smack talk is allowed in most sports. A player can get disqualified for it and I think most sports leagues have rules about it.
The only time I've seen athletes engage in smack talk is during boxing competitions on TV. And I personally find it childish and distasteful. I know that in most if not all school leagues, there are rules limiting or forbidding smack talk.
I also don't think that it is seen very favorably online. It might be allowed on sites where there is no oversight. But most public forums also have rules about not insulting members of the forum, so smack talk is not acceptable there either. Moderators can ban members who engage in it.