Have you ever noticed that the phrase, "my door is always open" is usually said by douchebags? "My door is always open" indicates that this person is always available to you, which is never the case. The people who are actually always available are hiding in their offices with the door shut (if their office even HAS a door), because their constant availability has indicated that they can handle EVERYTHING while the "my door is always open" pricks are gallivanting around town without a care in the world.
If you ARE one of those d-bags, you can prop your door open with these beautifully-designed Ski Slope Door Wedges ($15, Svpply). The rest of us poor schmucks will be hiding under our desks.