Properly written papers about such studies outline how participants were selected and surveyed. Some biases will be obvious enough to not be explicitly stated (e.g. phone and web surveys only get the attention of certain kinds of people) while other issues and biases are usually thoroughly discussed. This isn't a new issue and something the social sciences have known about and been dealing with for a long time.
And it is important to remember that often summaries and what gets reported about studies drops a lot of the details and qualifiers. I've seen numerous times that a news story makes a study look horrible, and readers had a shopping list of things that they thought the researchers were too stupid to think of. But if you look at the actual original paper written by the researchers, you see they addressed or acknowledged all of those points, and they made actually much narrower claims than the simplified news summary lead to believe. (And political polls can be whole another can of worms, especially when politically motivated, but only publishing results without the methods to see potential problems yourself.)
Properly written papers about such studies outline how participants were selected and surveyed. Some biases will be obvious enough to not be explicitly stated (e.g. phone and web surveys only get the attention of certain kinds of people) while other issues and biases are usually thoroughly discussed. This isn't a new issue and something the social sciences have known about and been dealing with for a long time.
And it is important to remember that often summaries and what gets reported about studies drops a lot of the details and qualifiers. I've seen numerous times that a news story makes a study look horrible, and readers had a shopping list of things that they thought the researchers were too stupid to think of. But if you look at the actual original paper written by the researchers, you see they addressed or acknowledged all of those points, and they made actually much narrower claims than the simplified news summary lead to believe. (And political polls can be whole another can of worms, especially when politically motivated, but only publishing results without the methods to see potential problems yourself.)