Note: Looking for a cloud host? Check out NetHosting’s Cloud Virtual Hosting plans and get the best deal around!

Dropbox continues to attract new users.

Cloud storage service Dropbox has recently hit the 100 million member mark, according to Forbes. Their user base has doubled in size over the last year, and continues to climb. And in the period of just one day, over one billion files are saved to Dropbox servers.

Dropbox is a free and paid service that lets you synchronize the storage and sharing of your photo, document, and video files. Basic users are granted 2 gigabytes of space which can be accessed from any desktop computer, laptop, or web-enabled mobile device. Referring friends increases free customers’ maximum storage by 500 megabytes up to 18 gigabytes total, and Dropbox also runs occasional promotions with even bigger rewards.

In fact, they are running a promotion right now that they’ve named The Great Dropbox Space Race. The invitation is for university students to register with their school .edu email address for additional storage space for the next two years. Users are then encouraged to share the promotion with their classmates, because each university gets group bonuses as more students sign up. The maximum reward amount is an additional 25 gigabytes of storage space. Not bad for a free service! The university with the highest number of “space racers” is the National Unviersity of Singapore at nearly twenty-thousand participants.

Dropbox is able to afford such a venture because they have had steady conversion from their free customers to paid plans since they began in 2007. And when the two years of potentially huge storage runs out for these students, you can bet that a lot of them will take the plunge to the $9.99 per month service. Their revenue from 2012 is estimated to be around 500 million dollars.

As for competition, no one else does things quite like Dropbox. According to co-founder Drew Houston, “All these big companies are busy punching each other in the face. They’re going after each other’s core businesses. Google is into social networking. Facebook wants to be into search. That’s good for us. The good engineers at those companies want to go on the front lines of these galactic battles rather than in our space. That, more than anything else, is why we have a unique opportunity.”

To find out more about what makes Dropbox tick, check out our case study on the service here!