business idea or business plan

Which one is more valuable - the business idea or the business plan?

Many of us can relate somehow - it's like the question we ask about "what came first, the egg or the chicken?" And which one is more important in the process?
In today's modern world of business & entrepreneurship, a creative mind and innovation is crucial to developing a business idea and pursuing a plan of action to make it happen. I thought to myself.... would my business idea work even if I have a weak business plan? OR, would a good business plan make a business idea <> work?
Then what comes to my rescue is the centuries old saying learning by doing. I decided to study few recent start up and tried judging them on my gut feeling and knowledge in the process i found a very interesting example of http://www.meracareerguide.com/
they started with what seems to be a common problem in India" educational conselling" and advice.
And in due process the content they developed is something to look out for as in
1.career assesment test
2.course planner
3.musings
4.career options
5.job hunt
and many more
it's definitely avery promising startup and something to learn from . It can rightly be called "ONE STOP DESTINATION FOR ALL YOUR CAREER NEED"
hats off to meracareer for creating such a promosing and effective tool to ease out the career decision maikng of students and guardian