To be clear, I was asking about legitimate use of multiple grants, since we don't know when we apply if we will get any of them funded, much less more than one. Also: as multiple people have pointed out, granting agencies like NSF, Wenner-Gren, SSRC, etc. already have rules and procedures so that you don't use two sources for the same expenses at the same time (most of them actually work with your budgets directly to help you figure out legitimate ways to use funding from more than one source if you secure it). In my case, I found out about one grant before another (both submitted during the same period), and then am now submitting for a third, which will cover some areas of the research that the others would not. Unless you flat-out lie, none of these funders are going to give you the full amount of the grant for the same project if you already secured funding from someone else; instead, they might give you a few thousand, particularly if they have different internal rules about what's covered (e.g., some funders pay for insurance and some don't; either way, it's good to have insurance). The fact is, that particularly for people doing research in expensive places like Western Europe, the maximum that any of these grants gives you on its own is not nearly enough to actually live and do research; budgets must therefore be artificially low to make a case for feasibility. Additionally, there are legitimate reasons to expand the scope of your project, do comparative work, etc. I hear the ethical argument at a broader level, but in this specific case I don't think there are any ethical issues with applying to multiple grants and if one is lucky enough to get more than one, proposing an honest and reasonable project that could benefit from multiple funders. At the end of the day, the decision is up to the funders and they are not idiots: they can generally differentiate between a legitimate, feasible proposal and one that is purely constructed to secure more money.