Also, any methodology problems can be mitigated by the fact that they did the same survey with the same methodology in 2017, and compared their results. You exp

Also, any methodology problems can be mitigated by the fact that they did the same survey with the same methodology in 2017, and compared their results. You expect to get better accuracy by asking people then and now "do you use Facebook?" than by asking them now "do you use Facebook, and did you use it two years ago?"