HotelTonight, the last-minute hotel booking app, has launched a new user review feature called Snap Your Stay.

Rather than the text reviews familiar at other travel sites, this feature takes advantage of mobile users’ propensity to snap photos of their hotel stays and share them on social media.

Users take six photos and post them at HotelTonight, Facebook or Twitter.

“The process of taking photos is more fun than writing a review, which feels more like homework,” says HotelTonight CEO Sam Shank.

Since we last checked in on the startup, which launched a little over two years ago, it has grown substantially.

It is now active in nearly 100 destinations in 12 countries, with over five million downloads to date on iOS and android. It has some 2,500 hotel partners worldwide, over 30,000 folllowers on Twitter and more than 250,000 Facebook fans.

It’s opened a London office to oversee its expansion into nine European countries, the latest being Spain and Italy.

Meanwhile, in a sincere form of flattery, travel industry giants Expedia and Priceline have added "last-minute deals" to their sites.

The Snap Your Stay feature is a good example of how entrepreneurs like Shank are rethinking and attempting to optimize for mobile devices.

“The number of taps that it takes for a user to snap and share six photos in our app is about 20,” says Shank. “That’s orders of magnitude easier than writing a review.”

Special filters in the app help the user perfect the lighting in the photos.

HotelTonight displays the best deals at the top of its feed for each city, which translates to six or seven each day in San Francisco. "Once those sell out," Shank explains, "we show the next group, and so on until the inventory is exhausted."

The company, which employs about 100 people, works with about 20-30 hotels in most markets.

Shank says that about 50 percent of HotelTonight's users report they would not have booked a hotel without the app, indicating it causes a lot impulse bookings. He says there's a high volume of such bookings in the Napa Valley, "where there's also often a reason by the end of the day to perhaps not want to drive home."