Here's an hypothesis:

The success story is central to both program evaluation (on the not-for-profit side) and product marketing (on the for-profit side) just as the brand story is central to corporate marketing. It's the core promise of the program/product ... the "value equation" that funders/purchasers use to make a decision about what they're getting from their investment.

Success stories (well done) are peculiarly transformational.  They are how we communicate the potential of an idea or solution within a community.  They are how we scale up positive outcomes to achieve a significant impact. 

We're hoping to develop (and borrow and reference) a useful methodology around using social media to develop and transmit success stories.  The storycapture.org site is just a tool that may be useful as part of the process.  But the value of success stories transcends any one tool or methodology, and we hope to share insights across a wide range of fields, industries and disciplines.