Here in Utah, most streets are numbered in a very logical grid system based off the Mormon Temple. 7000 West, 7800 South, etc. So, coordinates wise, 1234 West 7800 South is an address west of the temple, and the street its on is 7800 South (which is, gasp, south of the temple). Most of the map sites completely butcher this by using names, which are used in a secondary fashion around here and often not on the street signs, for directions. So if someone gives me an address, and I use mapquest, it tells me to turn onto streets by name. Most don't even have the name on the street signs. Ironically, the streets that we use names for, mapquest will assign the highway number in the directions. Turn left on Bangerter hwy...mapquest says turn left on Higway 154. The sign says....Bangerter highway.
Also, mapquest and yahoo often give directions to just drive across town, completely ignoring the highway/freeway system.