I'll admit that I'm not familiar with usage of S/MIME in e-mail, so I don't know how invasive usage of that is going to be. However, it seems clear to me that if introduction of S/MIME and X.509 will impose restrictions on what e-mail clients can be used, one is intruding on an area where there may be emotional reactions, and the proposal as it stands does not really address those issues.
How useful that emotions are used to define what the best solution might be rather than carefully thought out analysis of what the best option rather is :-) You don't add any weight to the argument with this point.
I'll concede, though, that on the WEB, it would seem that X.509 usage in the form of https is the only viable option, but then again, that's not what we're discussing here, right?
No but it highlights one of the reasons why X.509 might be the better choice. Neil.