As discussed in other posts, most Android devices don't support recording calls. Recording AudioSource.VOICE_CALL does though work fine on my Samsung Galaxy S2.
Does anyone know if supporting this is Google's new trend, or it's just a feature specific to SGS2?
I don't believe that Google is moving towards recording voice calls. In fact, I think they are probably working on ways not to allow this due to large security issues. Speaking of which, some recent news that happened a few days ago reports of such security flaws. I don't think that using AudioSource.VOICE_CALL was meant to be used in this way. Hope this answered your question.
Update: News link from 2011 is unfortunately broken now. Sorry about that.