Great for situations where you want a high signal to noise ratio like a discussion forum.

Needs adjusting for international use - overseas mail often takes too long or is prohibitively complex in less developed countries.

I love the idea of up-front friction to keep out not just the insufficiently motivated, but what else can you make people do to weed out disruptors or non-contributors? “Along with your application please include a printout of an example of excessively pedantic commenting, as well as an example of least-charitable interpretation of others’ comments that you’ve observed on other forums“?