You do indeed get an answer aligned with their interest, which is often useful (not perhaps in your example), as that is generally the point of the survey (to find out what your respondents think).

You need to pick your respondent cohort carefully if you are trying to ask a question of opinion (particularly more so than when asking a question of fact) to eliminate bias in your cohort. So in your example, rather than surveying particle physicists, you would look for another group of interested parties (e.g. a range of tax payers or non-specialist funding bodies) who have a vested interest (in this case in how their money is spent).

My work, for instance, revolves around surveying doctors on their experiences of medical training and career needs/aspirations. The vested interest of our participants is hopefully clear (influence on their training/career/work environment). We ask a wide range of factual and opinion based questions, eliminate biases (or segment responses on biases) due to various factors (e.g. location, age, gender etc.) and report our findings in the context of our cohort, i.e. "these are the experiences and opinions of doctors".

In short, you are right, you need to consider the makeup of your cohort and also how you report your findings in respect of that. Having a vested interest doesn't necessarily mean being biased, and sometimes that bias is what the survey aims to report on. In a survey like the google ones, that bias is money/free content, and thats all you will discover.

I think he's meaning they will actually pay attention to the survey, and then asking questions that aren't as black and white as the one you posed.

Asking particle physicists would they rather have X than Y when both are relevant to their interests would yield better results than asking a butcher particle physics-related questions and dangling a carrot in front of him for clicking through it.