To shake or Not to shake? FIDE answers the Question.
" Any player who does not shake hands with the opponent (or greets the opponent in a normal social manner in accordance with the conventional rules of their society) before the game starts in a FIDE tournament or during a FIDE match (and does not do it after being asked to do so by the arbiter) or deliberately insults his/her opponent or the officials of the event, will immediately and finally lose the relevant game. "
There must have been noteworthy incidents of boorishness on the international circuit for FIDE to incorporate such a rule into their code. I remember watching a video of the first match-up between Kramnik and Topalov after their world championship match in Elista, and neither one of them extended a hand. Kramnik, tactfully, arrived at the table with a small cup of coffee in one hand and a bottle of water in the other. How could the fellow extend his hand? Now, I feel that was brilliantly planned and I don't mean that in a critical or sarcastic way. Kramnik, himself, stated in an interview that he does not want anything to do with Topalov and Danilov as much as possible. As for Topalov, he had nothing in his hands, and he did not extend any of them anyway. Inspite of this, I think that they were still very civil with each other because no OTB trash talk or tantrums took place. They just ignored each other.
The way I read the rule is that a player should extend his/her hand for a handshake OR greet the opponent in a courteous manner. People have commented that they have personal reasons why shaking hands is not a good idea for them. They have concerns about cleanliness, catching colds, arthritis pains, and so on. Well, then, if ever you are in a FIDE event, just give your opponent a warm " Hi and Hello " and you've conformed with the law of FIDE. Bear hugs are not required, by the way.
http://www.fide.com/news.asp?id=1391