Michael Quinn related some unethical missionary practices that went on during his mission in his PBS interview:
http://www.pbs.org/Mormons/interviews/quinn.html
Quote from interview below:
How did the church grow so fast and what kind of pressure came along with that?
Well, this was a terrible thing. I was a missionary, and my experience is true of all LDS missionaries. You're separated from your family, very often for the first time in your life. You're in an unusual environment. ... And then to be put under the situation that if you're really going to please your mission president, who's your kind of substitute father, you've got to come up with high numbers of baptisms. ... Missionaries just threw ethics to the wind, and they did whatever was necessary to do to please their mission presidents. ...
When was this and what was the scope of the problem?
This period of tremendous growth, coupled with missionary abuses because of the pressures put on them, was happening during the period basically from about 1953 to 1960, and it was happening throughout the world. ...
One of my missionary friends in England came to me one time when I was talking negatively about baseball baptisms, and he said, "Well, you know, I'm a baseball baptism. But," he said, "in Louisiana we called it beach baptisms." ...
The missionaries would come to them in these backcountry areas and say: "We'll take you to the ocean. You've never seen the ocean before. The LDS Church will pay for us to take you to the ocean so you can have a beach trip. Tell all your friends above the age of 8 to come on this trip." They'd hire these buses, and they would drive the hours necessary to get from the hills of Mississippi or Alabama or Louisiana down to the beaches. Then when they were down into the beaches, these missionaries would dunk these kids into the surf, and the kids thought they were just playing. Then the missionaries would be writing down names and keeping records, and as the kids were going back during the several-hour trip, then the missionaries were talking about religion, and they found out that they were members of the church. ...
The mission presidents were in competition with each mission to get the highest numbers of mission baptisms. Then every missionary within a mission was put under this kind of pressure, and it resulted in these worldwide abuses. ...
So.. did things like this go on in the missions of others on this list?
In my mission (southern Peru) there were TONS of inactives, especially among the poverty-stricken native American popualtions, who had been promised refrigerators and stoves if they were baptized, then were disappointed when the promised appliance didn't materialize.
Also, there were many families who hated the missionaries after they had flirted with their daughters and promised to marry them and bring them to states - but they never heard from them after they returned home.
Ktall