I was aware of BART's actions before this, and now that there is going to be an organized rally in defense of free speech, I will attend...peacefully and in red.
I forgot to mention, this term includes purchase redirects to mobile Safari. The Kindle app accomplishes this but it is fairly disjointed. Recurly mobile payments (http://recurly.com) has a solution that is seamless and redirects back to the app upon checkout completion.
Upon review of the iTunes Connect EULA in fall 2010, 3rd party in-app purchasing is possible as long as a pre-existing service which requires payments exists prior to the release of an app. For example, Evernote does/did qualify, because its service exists outside of the iOS app. Zoosk app may have this implemented — http://d.pr/oc2F