This is possibly nothing and might not be related to Diablo III beta testing. However, previous pre-beta preparation shared similar type of maintenance oddities.
While checking my Battle.net account for any new changes, I noticed my StarCraft II links were completely gone. I launched StarCraft II: Wings of Liberty and downloaded the latest patches. The StarCraft II Battle.net server seems to be operating normally, but when I go to the Battle.net Account page -- StarCraft II is simply gone.
It might be completely unrelated to Diablo III beta testing, but I just had to inform something is going on and that Battle.net developers are doing some tweaks behind-the-scenes. There doesn't seem to be any Maintenance notices in the Battle.net Status forum.
Update: Two hours later (10:00pm EST / -5GMT) the Battle.net Account page now shows the StarCraft II text, icons and links. I was checking every 30-40 minutes, and it was all gone until now. Mysterious unscheduled Battle.net maintenance. Surely going to hype some people up. The Blizzard Customer Service twitter, StarCraft II Twitter, and all forums are silent on the matter.