At Safecast.org, I pushed our team to use the CC0 public domain dedication for the data that we are collecting through our radiation measurements instead of a Creative Commons Attribution license, which would require by law that people give us attribution. The reason is that we must give people the flexibility to use the data as part of an analysis or service that would be encumbered or impossible with the attribution requirement.
Many large data aggregation projects would fail with the attribution requirement. For instance, if each person with each sensor had to be attributed and our data got rolled up into a massive analysis of all historical sensor data to find megatrends, it would be impossible to provide attribution to every single provider of data. Open data is essential to allow people to write software that uses the data freely and combines it with other data.
Providing the Safecast data under a CC0 public domain dedication does not, however, make it ethical for people to take all of the data from Safecast, re-skin it and present it as their own. To understand why this is true, one must understand the difference between what is ethical or normatively true and what is legally true.
Plagiarism is when someone takes someone else's work and represents it as their own. In many cases, this is not illegal, just unethical. For instance, if I take someone's idea and use it in my academic paper, or take Safecast data and make it look like I did it all myself, that would be plagiarism, not a copyright violation. It is unethical, but not necessarily illegal.
On the other hand, using a picture of Mickey Mouse in a presentation could be argued as an illegal copyright violation, but most would probably argue that it is ethical.
It's very important to distinguish the difference between legality and ethics. Most of our society and our behavior is driven and guided by social norms and ethics. Just because something is legal, doesn't mean it's ethical.
In other words, just because you dedicate your data to the public domain, it doesn't mean that you don't have the ethical right to ask someone using your data to cite the source of the data on their website, just like you'd ask someone using your idea in their academic paper to give you credit for if they'd gotten it from you.