I've had both types of encouters. I used a fawn in distress call prior to the season a few years back just to see what would happen and let me tell you I was shocked. I set up with a buddy behind some old laydowns and started wailing away on that thing. Not 2 minutes later a doe comes busting through the woods right at us full speed. She gets within 5 yards and stands there looking around frantically. All I could think was holy crap...this thing worked! that being said I have yet to see it work this late in the year. The yearlings I saw Saturday were decent size. I just think in my area the doe really hear that sound much now. In the early spring when the fawns are still really small it's a more common sound.
As far as bear go I talked to a guy who had one come out at him at our camp. He was fly fishing along pine creek here in Pa when he noticed a doe and a real small fawn accross the creek (100yards). He thought it was a good opportunity and went to his truck where he had his hunting gear for predator hunting and pulled out a distress call just to see what the do would do. He started calling on it and within seconds a large black bear stormed out of the weeds just updtream from the deer. The deer bolted and the guy put the call down quick. I guess he was stalking the deer and when he heard the call he figured it was his chance. Unfortunately black bear and coyotes are our two leading killers of fawns out here.