Location-based services lure users, advertisers, investors

If there were any lingering doubts about one of the hottest new technologies, a big investment and burgeoning membership numbers are proving that location-based services are about to go mainstream.

Last week, Foursquare raked in $20 million in venture funding. The ultrapopular Foursquare, which offers a free application that lets people flag where they are, whizzed past the 1 million-member mark in April and just passed 1.8 million. Services including Gowalla, Loopt and Where are being embraced by mobile-device owners to shop, communicate, socialize and play games. Their total number of members runs in the millions. Meantime, Google has aggressively pushed its mobile social network, Latitude, and Facebook is expected to unveil location features this year.