How to protect the idea of a launched website from possible competitors?

We have just completed and launched our web based project and we are preparing for our marketing strategy after that we are sure we will get quite enough attention and users. After researching for almost 6 months, I am still sure its the only unique website of its kind.
My question is, can I legally do something to protect my idea from being copied by possible competitors?
What can I do if someone else really likes my idea and he/she decides to make same or similar web based project? (Note: it's not an app, it's a website where users will come and use the site same like, couchsurfing, facebook, linkedin but ideally totally different)
Another example is: If we make same or similar to twitter then, what they can legally do to protect themselves?

I am not sure an idea would be patentable. All your suggestions are welcome.

Thanks

Easy: while it's obvious to you that your site is great, most people will not be impressed, on the contrary. People don't copy ideas, they copy success. So yes, once your site becomes big and popular, people will want to copy it. Your protection is that by then, you are way ahead of them, and as long as you continue executing well, they will never catch up.

Alain's point is a good one.

• In any area of industry, if you succeed, others will copy your success. The first thing that you should do is secure a patent. If your idea is original and you have a working, it can be patented.

Step 1: Patent protection, and why it's necessary This gives you a level of protection that is mostly focused on keeping someone from copying your source code, building their own version of your server-side backend, and selling pretty much the exact same service, possibly, most dangerously, with the same front end. If this is done, you run into a few pretty big problems:

• users may be tricked into using that service, which may be a scam, or at least, will be profiting from your exact work.
• That site can patent YOUR code, in certain situations, and you may be legally pursued for using "someone-else's" patent. With the patents, it's pretty much the first guy to the office who gets the patent. Even if you can prove that you had the idea first, if you can't prove that the other side got the idea from YOU, he's safe.

Step 2: Competition The next thing, as Alain mentioned in his answer, is that there is a step 2 to all of this.

In all areas of industry, this is shown. Someone comes up with and patents an idea, and soon, hundreds if not thousands of others will rebuild your idea, just a little bit differently, and use your idea to make money. These copies and modifications then become competition.

Summary The key is to keep developing your idea and stay ahead of this competition.

Constant Genius: Great ideas don't define greatness in a leader. The ability to see problems clearly, ask the right questions, and constantly discover the right answers is what defines a great leader in industry.

Example: We see this in Steve Jobs, Bill Gates, and countless others. Steve didn't invent the displays that brought Apple to it's early rise. He saw Woz with a solution to a problem that the world didn't even recognize. And he lead that idea to completion. Great, +1 for Steve, but then what? If he didn't come up with the next big thing, he'd have gone down in less than a decade like so many other one hit wonder minds. He envisioned the iPod, the Mac, both hits. So he stayed ahead of the competition once more. But then what? If Steve didn't bring us to the iPod, someone else would have. Others did, in fact. But no one succeeded, because by produce with such regularity, ideas of genius, Apple was ahead of the competition and will remain that way until they stop producing ideas of greatness with regularity. It's the same story everywhere in industry.