In an attempt to lure more users under its fold, popular location service Foursquare on Monday updated its iPhone app with the sought-after ability to post comments and mark your places with photos.

The new photos feature lets you attach images to your check-in posts so your friends can check out a certain place visually before actually visiting it.

The company stressed that the images you attach to check-ins are only visible to your friends and the networks you share to, like Facebook and Twitter. However, you cannot yet share your photos from the Foursquare app to Facebook and Flickr.

In addition to the check-in photos, you can also file an image as a tip or venue. The former comes in handy when you wanna "see dishes before ordering them" while the latter is for "figuring out if a venue looks fun," Foursquare said. Bear in mind that both photo types are visible to the entire Foursquare community.

Considering that photo sharing is by far the most popular Facebook feature, it doesn’t take a rocket scientist to figure out that the same feature could give Foursquare a huge boost in terms of visibility and popularity.

Comments, another new feature, are only visible to your friends, giving you means to voice your opinion or figure out what your friends are up to. Topping it all off is a new history functionality on the foursquare.com site that lets you access all the places you’ve been and check out your past photos and comments.

The updated iPhone client is available now from the App Store while the Android app will be coming "later this week," followed by WebOS and BlackBerry versions in January. The mobile client will roll out to the rest of the major platforms in early 2011, the company said.

You’ve been probably sleeping under a rock lately if you haven’t heard of Foursquare yet. Conceived as a service to help people check-in to the places they visit and share their favorite locations with their friends, it has become quite a phenomenon. When you think of it, the service owes its popularity to the fact that a similar feature had been absent for too long from the world’s most popular social network, Facebook.

In addition, Foursquare cunningly employs a scoring scheme that awards users for each check-in or a newly added place, turning the location service into a huge popularity contest among its users.

Source: Foursquare blog