the point you make about couchsurfing being a “corporation” – albeit with a B “certification” – and not a “benefit corporation”, does make a big difference indeed,
so much so I feel like underlining it – quoting from the article you mention :

http://charitylawyerblog.com/2011/01/15/b-corps-is-not-a-new-legal-form-by-keren-g-raz/#ixzz1XCmd10l9

“The key difference is that the law requires a third party assessment ( for a “Benefit Corporation”),
whereas B Corps is – only –
a certification.”

…

“Why the difference is significant:

• One can be a B Corps and yet be incorporated legally as a C corporation, an LLC, even a sole proprietorship. In other words, a company can be certified as a B Corps without ever incorporating as a benefit corporation

• One can be a benefit corporation under Maryland law without being a B Corps. The Maryland law does not require that benefit corporations be certified as B Corps. Rather, it requires that benefit corporations’ social and environmental performance be assessed by an independent third party that makes publicly available or accessible the following information:

1. The factors considered when measuring the performance of a business;
2. The relative weightings of those factors; and
3. The identity of the persons who developed and control changes to the standard and the process by which those changes were made.”

And yet Couchsurfing is not even a registered Benefit Corp
(http://en.wikipedia.org/wiki/Bcorp), but still a normal C-corporation
http://www.bcorporation.net/index.cfm/fuseaction/company.report/ID/5e086197-f44e-4448-9519-5e35d5bde1e2

Corporate Structure: C Corporation
Ownership: Private

See als: B Corps is Not a New Legal Form
http://charitylawyerblog.com/2011/01/15/b-corps-is-not-a-new-legal-form-by-keren-g-raz/

See also the discussion on the CS-group
http://www.couchsurfing.org/group_read.html?gid=45507&post=10059584