While I believe there should be over-sight to these types of attacks, if you're an American and you choose to hang out with American hating terrorist in Yemen, or where-ever, then you're asking to get killed by a drone. Seriously, my parents taught me about guilt by association. It's really that simple.
Again, there still needs to be over-sight and review to this process. I don't believe in giving the President or the Military or any part of the government this type of power without scrutiny.