[Dylan16807]

It could theoretically give access to contacts via a contact-chooser button without ever letting the app get to the list. Much like you can upload a file on a desktop browser without letting the site see your list of files.

[falling]

That limits functionality quite a bit. Say you want to write an email or messaging client (K9, Handcent), your solution prevents you from doing name/address autocompletion in the To: field.