"Back in the day" it was strongly suggested that the Dungeon Masters Guide and the Monster Manual were solely the province of the DM. Whether or not this was ever actually true or not is open to debate, but what is certain is that 3E and 3.5 completely tossed the idea out the window. The DMG included information important to the players -- prestige classes and Leadership and magic items/item creation rules -- and certain mechanics in the PHB (animal companions, druid wildshaping and summoning spells) made the MM an indespensible resource for half the classes in the PHB.
I say it is high time to go back to "restricting" the DMG and MM to the DM -- and by that, I mean put the information the players need in the PHB: stats for common animals and summonables, rules regarding feats like leadership and item creation, etc... A new edition -- especially one with so much change -- is the perfect time to get even grizzled veterans' "sense of wonder" back. Knowing all the secrets of the game and its meta-setting, though, don't allow that.
I say it is high time to go back to "restricting" the DMG and MM to the DM -- and by that, I mean put the information the players need in the PHB: stats for common animals and summonables, rules regarding feats like leadership and item creation, etc... A new edition -- especially one with so much change -- is the perfect time to get even grizzled veterans' "sense of wonder" back. Knowing all the secrets of the game and its meta-setting, though, don't allow that.