When looking at the MultiCollider drop down I'm not seeing my accounts on Code Review or Area 51.
I could swear I saw my Code Review account there the day I created the account, but since then it seems to be missing.
The only reference I could find on the intended behavior of the MultiCollider:
Your current site appears at the top, along with any relevant meta, chat, and blog links. Stack Overflow gets a careers 2.0 link. Immediately below, in a new condensed format (you certainly don’t need descriptions if you’re participating in a site already), you’ll get a list of all the sites that you have logged into, in order of reputation. Finally, you’ll find the full alphabetical site list with descriptions, searchable by title, URL, and description.