[MaulingMonkey]

> If any survey of any size can be ignored on the basis that the sample is not random, then how is any survey meaningful?

One can take efforts to make the sample more random. This is part of the reason why the U.S. Census is legally compelled, for example - to try and reduce self-selection bias. Or the push for mandatory standardized tests in schools.

One can contextualize the results. Applying, say, English literacy rates from a U.S. Survey to China is obviously going to be totally wrong. Applying a developer salary survey at Google to Game Developers is going to be totally wrong. But within their context, they can be more accurate. Outside of their original context, the survey can be re-run.

> ie. Isnt this just a convenient excuse to deny that a survey is meaningful?

While convenient, it's sometimes also inconveniently true that a survey isn't terribly meaningful, or isn't in the context it's being reapplied in. Statistical stuff is hard, a lot of surveys are bad, and while you can make some reasonable guesses and extrapolations, it's worth doing so with a giant grain of salt.