Discussions regarding players being put on the clock are comon. There are many conditions that might be deemed improper, that are not specifically covered under RROP or the TDA or any other rulebook. They are defined as comon courtesy, and are covered in the category of "etiquette," or defined in house rules.
I am in favor of the dealer calling the clock.
According to the rules, a player has one minute to act on his hand (after being put on the clock), followed by a count-down from ten to zero, before he has to act. This is after a resonable (ridiculous) amount of time has passed. I've read that two minutes is what is considered resonable. Imagine a dealer, that is working 30 minute down time at each table. During that "down" a good dealer should get out 17 to 20 hands. In a ten handed game of hold'em, with four betting rounds, if only half of the players took that much time to act, the dealer would NOT complete one hand! All of the on-line poker sites figured that one out. After about 15 seconds, you'd better act on your hand, or it's dead!
I also believe that the floor should step in and make it very clear, to any player that delays the action, that his time to act will be drastically reduced in the best interest of the game. I admit, some hands warrant more time to figure than others, but we are talking about the repeat offenders. Consider the effect it could have on a tournament that goes "hand for hand" when down to the final tables?