alt Hacker NewsOne of the most important "con"'s is that without controls, fewer people will allow their data to be included in the data sets.
One of the most important "con"'s is that without controls, fewer people will allow their data to be included in the data sets.
That's a very important point. The people who opt out first are typically not a random fraction of the population, and this makes it much harder to make any analyses with the resulting datasets: it gets very hard to know if your analyses are representative of the population, or not.