2.) One is grocery-blocked after making the foolhardy decision to get in line behind "that" person.
3.) One is grocery-blocked when a cashier kicks you out of line for they are going on break immediately after ringing up the person in front of you.
2.) "that" person: the one person who needs fifteen separate manager price-checks, leaves the checkout line mid-transaction to wander back to the bread aisle and make an exchange, haggles the cashier with competitor coupons and grievances concerning dented cans, then proceeds to pay entirely in pennies, or wampum.
3.) "I really wish the cashier didn't wait until I was next in line to turn off the register light and grocery-block me with the news that the lane is closed. Better yet, cashiers should be stripped of their right to deny service to anyone that has committed to their line! Even better yet, cashiers shouldn't get fifteen minute breaks. Best yet, cashiers should have to carry all of my groceries to my car, and do it smiling :)"