[theorique]

In the UK, Tesco and other grocery retailers do this. I've seen this in place in the USA at the Whole Foods at Columbus Circle (an enormously crowded store that moves along well).

Based on these data points, it would seem as though more crowded places use this optimization.

[afiler]

Lund's (a snooty high-end grocery chain in Minneapolis) set up their new store in Old St Anthony (a fairly high-density area) this way too.