Burping v/s bleeding hydraulic disc brakes: is it safe? I found a method for burping (get the air out of the circuit) hydraulic disc brakes in YouTube (see here). The method is: 

1) Rotate/move the hand lever assembly until the reservoir cap is facing up and at level. 

2) Take off the reservoir cap. 

3) Slowly squeeze the lever repeatedly, until no more air bubbles come off.

4) Refill the reservoir with brake fluid.

5) Put the cap back on and return the lever assembly to his normal position.

To me it looks far more simpler than the standard procedure, and can be used in an emergency on the road (Obviously, it doesn't apply for replacing old fluid).

What problems can you see with this method?
You aren't assured of getting all the air out of the system.  If your bubbles are further down and this doesn't remove them, you may actually introduce more air than you remove when you replace the cap.
You won't effect a fluid change this way.
You won't replace the crush bolts and other pieces swapped at the true bleed that are        potential sources of failure.
If something happens and you bump/spill some fluid, you are SOL for replacing it.
If you have a leak that has introduced air, this may not help any. 


Not to say this isn't a decent method to try for a home mechanic as an initial troubleshooting step if you are into it.  It may be done faster, with little to no cost, and may help some issues.  However, you are correct, it does have several shortcomings.