"I had that idea years before they did it."
It's a common statement amongst developers. The problem is that they either failed to execute or just never acted up on the idea in the first place. Working alone can be a very daunting task. A sole developer can cut a very lonely figure and often as a result failed startups are a dime a dozen. My advice: just fucking do it. Words to live by though often words words to regret. Work on your idea one line of code at a time, one meeting at a time, one night at a time.
Missed opportunities happen all the time and will always continue to occur. Get out and meet like minded people at networking events like Ruby Oceania and Silicon Beach in Sydney. One of my resolutions this year is to be much more open for opportunities of any description. Saying yes to new chances, meeting new people and working on new ideas. Follow up with chance encounters, you never know what path it will lead you down.
Make 2011 your year to shine because no-one else is ever going to make it for you.