The acid test of a vision is whether or not you can actually see it? You'll know you've struck upon something worth pursuing if you can paint a picture of the outcome for yourself that you can clearly see in your minds eye. If a group of people are involved you need to paint the picture so that they can see it too. It then needs to strikes sufficient cord that makes you (and them) think "I definitely want to be a part of that".
So when you're creating a vision the acid test is "Can You See It?"
Ken Rudge