When hiring people to do stuff, it would often be convenient to provide partial access to various services. For instance, I'd like to hire someone to post some HITs and Mechanical Turk for me, but I don't want to give out my AWS access keys. It would be great if I could create a sort of limited access token that would let someone spend up to say $10 of my money, that would be good for the next week. Or I'd like to get a token that would allow someone to edit a particular blog post, that would expire in a couple days.
It would be convenient to create access tokens that are not specific to a particular person, sort of like the edit-URLs you can get to a Google doc. This would make them easier to give hired hands, without needing to exchange account information.
I feel like the only way to do this would either be to convince companies to provide such limited access, or for some startup like ifttt to do the work of wrapping lots and lots of APIs, and being the trusted-middle-man for partial access.