Dealing with Internet research panels is like securing your house when you’re going away on vacation. There are all sorts of steps you can take to burglar-proof your home, but the plain fact is that if a burglar wants in badly enough, you’re going to get burglarized in spite of all your careful precautions. Police officers will tell you that the goal of burglar-proofing your home is not to make it impossible for burglars to break in, but to make it much more difficult for them, and therefore much less likely to happen.
Quality checks on Internet panels work the same way. I may not be able to ensure panel quality 100%, but there are plenty of steps I can take (and have taken) to make it a far higher likelihood that I’m getting good data.