So, this past year, I've tried 3 different business ideas. Project 1: This was a 4 Hour Work Week idea. I built a contact database for every hospital in the US, I put up for sale on a yahoo store and I pointed Adsense at it. I had done Adsense testing check for demand. It failed. I thought the from my testing I should have been getting 2 to 3 sales at $150 per sale each month while spending $100 a month on Adsense. I didn't get a single sale in 3 months. So, I lost a grand for the whole project. No big deal. I learned a lot.
Project 2: Social cute site. It was a reddit clone for cute pics (cats, dogs, etc...). I shut it down after 3 months, because I couldn't take looking at cute kittens that much. But, I took that code base and what I learned from it to start http://newsley.com .
What I've learned in each one has been invaluable. The argument of whether or not we should try to build a startup to succeed or fail is rather moot, I think. No one builds a startup to fail. But, after having failed at 2 business ideas, I still think it was very worth while. Ultimately whether my success rate ends up being %25 or %29 or even %5. It doesn't really matter to me, because I'm going to keep working at this until I do succeed, and I'm enjoying the process.