Up against the deadline for submitting new versions, I posted
http://tools.ietf.org/html/draft-masinter-mime-web-info-01
without carefully addressing your comment on the "applications that use this type" in what had been section 6.1 (in fact, the text in -01 is unfortunately incoherent.)
I was thinking about this, and wonder if the issue is really around the security considerations for sniffing and privilege escalation...
Content that allows hyperlinks to embedded content
-- which is (or is not) commonly automatically retrieved to display
E.g., html with embedded IMG tags
Content that contains scripting:
where script content can access the internet
-- with or without sandboxing
where script content can access the "local file system"
Content that is not intended to be scriptable
Buggy software can turn a JPEG into scriptable content which accesses the local file system, but it's "buggy"?
Turning text/plain into malicious content might involve attacks on the UTF8 decoders?
Note that some fonts are scriptable....
Larry
--
http://larry.masinter.net