That makes calling Apple’s Mini DisplayPort “proprietary” a bit of a stretch, but it’s also inaccurate to say that Apple took the connector from the spec, when it really didn’t.
Since there is no existing Mini DisplayPort in the VESA specification, Apple is contributing something new to the emerging technology portfolio that hasn’t yet been widely adopted. Mini DisplayPort may likely be used by other PC makers because it cleanly moves video standards forward while adding significant value in size reduction.
If other PC makers follow Apple’s lead, they’ll be able to deliver better graphics on their laptops using the superior signaling protocol used by DisplayPort and the more compact port Apple itself has standardized upon. If they instead choose to use the larger, full sized DisplayPort, Mac users will only need a physical converter cable, just as many Mac users today use DVI to VGA adapters or cables.
Apple’s lead is more likely to be followed now that the company is selling such a significant portion of consumer retail laptops, with roughly a fifth of unit sales and a third of the dollars spent on laptops. Those who don’t follow Apple’s lead will simply look behind the curve.