The main myth we discussed over coffee and biscuits back in the compsci staffroom was .. expensive as all hell on the computers we have now. (a good handwaving often used to say "one day, in the future, somebody will make it work")
Looking at it strictly from the outside, it looks like there's a ton of indirection to make it work. People usually do want revocable capabilities, which implies that every capability grant has one or more levels of indirection that go with it.
Indirection's costs haven't gotten cheaper in well over a decade.
Considering now every time you want to do anything on a computer you're getting interpreted code in a memory heavy gui environment to send a HTTP request over a TLS connection to a remote computer via a flaky wifi connection, the cost of doing an indirection might be relatively much less than it was a decade ago. In those days, you might recall, most of the time you clicked in your software it would be doing direct lookups in the machine's comparatively fast spinning disk using native compiled code in a gui api designed with a considered tradeoff between developer's convenience and memory usage - designed in the days when there were fewer developers and much less memory.
Of course, half the time those indirections will probably be remote to the server you're already waiting on...
