Queens / Brooklyn (other than Williamsburg) can be orders of magnitude cheaper than Manhattan.

Colma / South SF / Oakland are probably 30% cheaper than SF. Still cheaper, but not overwhelmingly so.

In my personal experience, there's a growing trend of developers working remotely from wherever they want. As that trend becomes more mainstream, I would expect regional differences in developers' salaries to shrink.

So I don't think the poll is meaningless without geography.

No I don't think so. You will have a lot of people who live in average places and have average salaries entering in their information, and any information generated from data is going to be representative, and reveal something about average salaries in average places. Then you might get a whole bunch of people in expensive places entering in their large salaries, and any information generated from that data will reflect that.

Then you will have a smaller number of people living out in the country, entering in their low salaries. Now there aren't too many of them so the affect they have on the statistics is proportional to their number.

Basically, you will end up with a number like 70k as an average salary. And that means something. It means the average developer, wherever he may live, earns about 70k. Sure people in expensive places earn more than that on average, people in cheaper places earn less. But that is obvious, each person in each place entered their salary and they all counted towards the average.

Now if everyone decided to try and correct away location, whatever that means, and scaled their salaries up to some arbitrarily expensive city, you might end up with a value like 120k, when in fact a vast majority of people are earning less than that. How is that representative? How is that useful or meaningful? Even people living in expensive cities are going to look at that value, and think they are earning below average when they aren't.