Singles, voyeurs, lonely people, barflys, and stalkers: The new Loopt is the iPhone app for you. The latest edition of the free, mobile-focused social networking service adds a very big, neat new feature: Loopt Mix, which lets you see who's nearby in real time -- mostly total strangers.

Like Facebook, MySpace, etc., you set up a public profile, with some sparse details -- photo, age, etc. -- and Loopt uses the GPS in your iPhone to figure out who's around. A potentially great way to meet people at a bar, flirt via email, whatever.

Privacy-types: It's totally opt-in and includes a very obvious privacy warning that you must click past to use. And it's clear when Mix is on -- transmitting your location -- and off. (See the red "On" in our screenshot.) So we're fine with that.

The biggest problem so far: The ratio is a little unbalanced, if you know what we mean. Anyway, worth a shot -- we'll keep testing it out and see if different neighborhoods/times of day lead to better results.

But our long-term question about Loopt and other mobile-focused social networks is still the same: Will they be able to attract enough people to be worthwhile social networks on their own? (Loopt CEO Sam Altman tells us the service has hundreds of thousands of active iPhone users.) Or will they die a quick death the minute Facebook and MySpace add location to their iPhone/BlackBerry/mobile apps?

See Also:
RIM, MySpace Link Up For BlackBerry App, Promotion
Location-Based Mobile Social Networking: A $3.3 Billion Market In 5 Years?
More Ads Coming To iPhone Apps: AdMob Expands iPhone Ad Network
Nokia Picks Up Social Networking Service Plazes