Trying to reply to a few parts of this nested thread at once, starting with OP:
>shawkinaw
>Goddammit. I really liked StartCom for free S/MIME certificates
Same. It came up over the last year in previous discussions when the covert acquisition began to come to light and I was forced to reluctantly dumb StartCom, but it really was a shame because StartCom's core business model was extremely sensible and doesn't seem to exist elsewhere. They essentially only charged for where there was a human time cost. So you could do automated verification (level 1) for free with decent time outs, and then upgrade to greater levels of identity verification (level 2 individual, level organization etc) building on the previous ones but in each case only the identity verification cost money, once verified you could request unlimited certs with that identity (since address ownership can be confirmed automatically). For email in particular it was quite nice.
As far as S/MIME vs PGP/GPG, it boils down to practicality in many situations.
>Why are you using S/MIME?
>It has less users than PGP/MIME, which is an impressive feat.
S/MIME has native transparent support on a number of major OS/email platforms, importantly including iOS (since iOS 5 IIRC). That helps solve the perennial general adoption problem encryption faces, ie., what happens when people using it interact with people who do not. With S/MIME there is some potential value just from signing and it doesn't require most recipients to install anything else at all.
I at least do use GPG in addition, and if Apple/Google/Microsoft/other clients all built PGP support natively into their platforms and email offerings then I'd stop bothering with S/MIME period. But as far as "how can I get many of my parents/family/friends to gain at least a little end-to-end email auth/security that they can use with minimal to zero additional effort on their part" goes S/MIME has remained valuable. Unfortunately. The entire state of email authentication in general is insanely frustrating (or even depressing), there are no great solutions right now despite the tech all being there. Use of S/MIME certainly has plenty of flaws. Right now though I've found it to still be a useful part of my toolkit and at one point I'd hoped that other places might adopt some of StartCom's innovations and ideas without the many warts. No such luck.