Both of our sons did the same thing (went from happily laying down and dozing off to standing in their cribs screaming at the top of their lungs when put down) at around their first birthday. (Our 13.5 mo. old still does.)
I think that it's just normal at this stage. The world is an interesting place full of keen things to interact with and bed is relatively boring in comparison.
Mitch seems to doze off after he has sufficiently exhausted himself telling us off and doesn't seem the worse for wear. You should be able to pickup the slight difference in his cry if it's something different (dirty diaper/leg caught in the crib/even painful teething)... I'm not sure how it works, but somehow it just seems to.
In any case, I *think* (this is only our second) that in a copuple of weeks, he'll stop the bawling as it doesn't get him anywhere.
Scott (Husband of S.)