How does it work? "In most cases, we match your IP address to a broad geographical location," engineers Jenn Taylor and Jim Muller wrote on the blog.

Does Google get it right? Sort of. Google's location detector decided that my desktop Mac is in . That's more than 35 traffic-packed miles from my home in downtown San Francisco. A search from my BlackBerry worked better, but . Instead of pointing me to the dry cleaner across the street, Google mapped a batch of cleaners in the city's financial district.

There's a way to adjust Google's targeting: Look carefully at the results map, and you'll see that after the title, e.g. "Local business results for dry cleaner near Dublin, CA," there's a smaller phrase in blue text: "Change location." Click it, and you'll be prompted to enter a "US city or zip."

Entering a city or ZIP code improves Google's local map, but it's still not 100% accurate. You can't enter your home address, only your ZIP code or the name of your city or town. Entering my ZIP code still missed my neighborhood by several blocks, pointing to dry cleaners a 20 minute walk away. Entering "San Francisco" once again mapped the city's financial district instead of my turf.

I got better results searching for businesses in my hometown of . After I entered the local ZIP code, Google mapped every florist and dry cleaner that I know of within driving distance.