Apple already has parental restrictions for people like you. The only way this is really a problem is if you're trying to hide something from a spouse or something.
I'm not trying to hide anything from anyone, but I can confirm that my entire family's iDevices show ALL content purchased from the App Store and iTunes. This includes everything my children have purchased as well as all the content my wife and I have purchased. On every single device we have RIGHT NOW due to this update. Automatic downloads is defaulted to "OFF" so none of the content is actually installed on the devices, but they are all visible in the cue.
What this proves is a single Apple ID syncs all media content across all devices regardless of who owns it (mom, dad, daughter, son). How about data and personal settings? What will that be like when iCloud goes live? I'm not sure Apple has this thing ironed out yet. Parents should have the ability to prevent content from getting "sync'd" or even displayed in the cue to certain devices because of who interacts with them (children).
In terms of multiple Apple IDs, this would negate the hundreds of dollars spent in iTunes as everyone else in the household would not be able to use the media content.
Apple allows families to share content via their Home Sharing! Even their website says households can share content on 5 computers and unlimited number of devices. So Apple allowed us to use a single Apple ID for years of purchasing media content to share in the family. Now, everyone has their cues filled with everything ever downloaded (to include all the worthless long deleted free apps).
The way it's set up now, iCloud is only good for a single user on a single Apple ID. Total Fail as of today's implementation. They need to provide an option to opt a particular device out of the sync for media content, and allow backups to occur per individual user, not Apple ID. In other words, we should be allowed to identify 5 seperate users within an Apple ID so all their content is updated and not affect the other users of the household.
From the Keynote, it looks like the @me.com required iCloud registration is only going to work with differentiate Mail, Calendar, and Contacts.