Well, it depends. I just said it to not make it more complicated. Depends on the version of UUID and some versions according to specification have fixed bits at some points. This can be dangerous for a key to have. Their generation could also not be as random as required for a key. In practice many now do not recommend just using UUID anymore because that could mean one could deduce some parts of the key.

If so, you should use version 4 of an UUID, not 3, not 5, just 4. Because by specification that is the purely random one. Version 3 and 5 use MD5 or SH1 from an input to generate the ID as far as I know. In the vast majority of cases this also doesn't matter, but better to be sure. Perhaps I used too much caps for the NOT. If you use a solid random generator you should be safe. Just don't rely on a ready-to-use UUID-generator for cryptographic purposes.