The responsibility for ensuring that shoppers complete repots without falsification lies soley with the MSP. That is why companies employ editors, fact-checkers, require proof of shops, and do random verifications. To insinutate that we, as shoppers, should take on that responsibility is unrealistic at best and a bit insulting (given the low margins we work on) at worst.
If falisfication is a concern of a MSCs (and yes, it very much should be - because although very few shoppers falisfy, it only takes one to loose a valuable client), look to your own internal policies and make sure you are doing what you need to do to ensure quality in the reports you turn into clients.
I would fall out of my chair if someone admitted on an open-forum that they had falisfied a report. If you heard someone discussing this at the conference, I would imagine it was a small group and they did not realize their discusson was being heard by a MSC rep (although this just proves my point that these people WILL get caught eventually). To answer your question, does it happen? Yes - it does. I have worked in this field a long time, and as both an editor and a client (end-user) I have seen 100% fabricated reports more than once (I can think of about 10 different examples I have seen first hand of totally 'made up' data). It also happens in other forms of data collection. In college I worked as a telephone supervisor in a marketing research firm, and we occassionally had telephone interviewers "make up" answers to surveys instead of calling people to get the polls done. This was in a central facility with supervisors RIGHT THERE looking over their work, monitoring their calls, and doing random call back/fact checks. Yes, they were always caught - but still for whatever reason, there is a small minority of people that think it is easier to cheat than it is to just do the work right.