Safe from copying unauthorized data to the drive? Safe from prying eyes (unauthorized access to the data they contain)? Even the CIA has rescinded their ban on the use of USB drives because they are just
Too difficult to control/manage.
Impossible to avoid use of (sneaker net is still a viable means for moving data between systems).
In any case, there are a number of techniques to keep people from copying unauthorized data to the drives, such as access-control lists to limit an individual's access to data they aren't supposed to get to. These can control what type of access they may have as well, such as viewing, printing, copying, copying to a mobile device, etc. SELinux has those capabilities (after all, it was developed originally by the NSA, and we know just how effective that was with Edward Snowden), as I think Windows does also, if enabled / implemented appropriately. As for prying eyes to data on the USB drive, you can easily encrypt the drive contents so that you need to have the key to access it. See www.trucrypt.org for that. There are also means to monitor what data is copied to movable media, sent via email, etc. In that case, you don't limit what people can do, but you can monitor it and deal with data breaches as appropriate, up to and including legal action.
Yeah mostly Windows doesn't always allow you to safely remove a flash drive or external hard drive. Is it? In these kind of situations , If you simply pull an external drive out of a running computer, you're asking for trouble. You might lose files, crash applications, or even ruin everything on the computer. But removing it safely isn't always as easy as it should be.