As already pointed out, posterous does have an API for that. Why on earth should posterous work on creating an app to do the migration? They have exposed the API and their part is done.
Frankly, the guys at posterous would have been big morons if they won't already have thought about it before starting their "migrating from dying platforms" campaign. It doesn't imply moral or ethics; it's simply business sense that when you are accusing others of something, you aren't guilty of the same charges.
Frankly, the guys at posterous would have been big morons if they won't already have thought about it before starting their "migrating from dying platforms" campaign. It doesn't imply moral or ethics; it's simply business sense that when you are accusing others of something, you aren't guilty of the same charges.