Airbnb ReferralsFirst Airbnb asked us to open our doors to travelers from around the world. Then it beckoned us to stay with other members who had also opened their homes to travelers. But that wasn’t enough. Now Airbnb wants your friends and family to join in too.

In announcing a free travel credit program Tuesday, Airbnb, the fast-growing social marketplace for travel accommodations, is moving to fend off rising competition by enticing loyal member to bring in new customers. The program rewards frequent customers with travel credits that are good towards a free night (or nights) at any space listed through Airbnb.

Airbnb is aiming to enhance the word of mouth that has fueled its success. Customers earn credits when a friend or family member books or lists a place on Airbnb. They get $25 for every referred person that books a trip over $75. For each referred person who successfully lists a space that gets booked, they earn $75.

The credits stack up, meaning customers can apply all the credits they’ve earned to the total price of an accommodation booked through Airbnb. The company even set up a page to track friends and family referrals from social networks like Facebook.  Airbnb automatically generates a coupon code for redeeming the credits.

The free travel credit program — along with a rumored $100 million total funding and high-profile investors like Ashton Kutcher — gives Airbnb an advantage over the growing number of competitors in the social travel accommodations market.

Last week, social travel startup Wimdu raised a comparable mega round of funding estimated at $90 million from Kinnevik and Rocket Internet, European investors known for putting money into “clones” of successful startups like Groupon and Zappos.

Airbnb has taken the threat of competitors very seriously — painting lesser-known rivals as deceptive scam artists and hiring an aggressive sales firms that ended up going rogue. But honestly, every piece of news about Airbnb suggests this is one startup that’s anxious to achieve success, which also makes it an attractive investment.

The company has achieved its measure of success by promoting its service as safer and classier than others — not to mention the 800 percent growth the service experienced in the last year alone. Airbnb has listings in over 14,500 cities in 184 countries, with over 1.6 million local homes booked, since launching in 2008.