I have 3 Google accounts: One @gmail address that I don't use but just forward onto a different address, and two @track7.org addresses that I do use. The one I normally use has my real name, but for things that are just out there on the internet for everyone to see (like YouTube videos) I don't want my real name associated with them. So I (on purpose) linked my YouTube account to my "anonymous" account when YouTube forced me to link in a Google account (I didn't want that).
Recently I reinstalled my laptop and found that YouTube won't let me sign in using my YouTube username and linked Google account password, even though it says I can do that -- instead it says to please sign in using my full e-mail address for my Google account. If I do that, then Google Reader / calendar / mail / etc. are all switched to my "anonymous" account.
My desktop is still on the install where I was logged into YouTube when it forced me to link it to a Google account, and there I'm logged into my YouTube account at the same time in the same browser as I'm logged into all my other Google stuff as my main account, which is what I want to do on my laptop as well, but it won't let me log in with my YouTube username, which I assume is the key. In case it makes a difference, my YouTube username and the part before the @ in the linked Google account are identical. If anybody knows how to get my laptop to behave like my desktop I'd be happy to hear it!