No.... plain GPS receivers doesn't work in buildings, in the woods. But if there is data network, then things change.
The new wave in LBS is merging A-GPS with social location information and other data.
Mobile phones have A-GPS (Assisted GPS) and other technologies, like Cell ID based locations and WIFI Hotspots information. By merging all this information, "positioning systems" that are not simply GPS anymore are getting much better.
A-GPS gathers Almanaque and Ephemeris data from the network, "making a weak signal stronger".
Cell ID (from the operators' cell phone antennas, BTSs) and WIFI help in between buildings, inside places by applying algorithms using simple techniques.
By gathering this information and crossing it, right now there can be pretty good results.
I'm using a Nokia E63 WITHOUT a GPS receiver. With the help from Nokia location based servers (supl.nokia.com) , I get pretty accurate location information without a GPS.
I'm a geek. I like sports :-)