I can't even begin to understand the sense of power and responsibility that must come with being entrusted with a squirt-gun full of sour cream, but apparently they don't give lessons on calibration.
Without fail, no matter what specific burrito I order, no matter how many times I say "light sour cream" or even "NO sour cream", there's inevitably one end of my burrito that is absolutely filled with the stuff.
I usually order twice as much as I actually want to eat, because I can reliably take a bite at one end or the other, determine which end doesn't have a mouthful of sour cream, and eat half of it. Then proceed to the next one, do the same, and toss the cream-soaked halves.
It's exhausting and wasteful but luckily one only gets a Taco Bell burrito craving every couple of months, when one's life is going on a spectacularly bad turn and you just want to eat the pain away.