We require some sort of positive attachment, more than a few toenails. We commonly see the post notched and the beam lagged into the post. There are also manufactured brackets for such connection as you described. I typically turn down more post frame connections due to an individual member of the beam being attached to the sides of the posts, non bearing, and through bolted with carriage bolts. This type of construction has been abandoned for decks, but contractors still seem to think its perfectly sufficient for 40′ wide post/frame buildings.