Why should the location-based social networks be worried about Google? Because its new Latitude product was able to gain over a million users in just a week, Google’s vice president of engineering Vic Gundotra told an audience at Mobile World Congress today.

Latitude is Google’s service which uses your location to place you on a Google Map. If you have friends who are also using the service, you can see them on your map as well, to see how close they are to you and read their status updates. It’s a similar idea to what startups like Loopt and Pelago’s Whrrl do.

While a million users may not actually seem like that much considering Google launched the service in over 20 countries around the world, it’s a pretty impressive number given just how clunky the service is right now. While the version running on Google’s Android mobile operating system works pretty well, as it presumably does on BlackBerry, WIndows Mobile and Symbian devices, a lot of users are likely accessing it through the desktop version, which is a mess. The main problem is that Google decided to make it a widget tied to services like it iGoogle homepage, rather than a standalone web app.