Seriously....
This is ridiculous! Privacy is a huge concern, and no one...I mean no one wants to have to buy Angry Birds for their kids and themselves. As steve Jobs said in the keynote. The apps in the Mac app store are available for all your macs, Lion included. So if that's the rules, then a family unit should not have to double/triple buy to preserve privacy. Everyone has their own opinions about honesty, and what's ok for their kids to see.
Bottom line. An app store account needs to have multiple logins associated with it, allowing for separate family members to purchase what they want, without the prying eyes of kids, or a jealous spouse.
Perfect example. My son just downloaded DNA dating free because he though it was a Pacman game. (look at the icon). Now if my wife finds that, I'm gonna have to answer for it, although it's not too big of a deal...just a hassle.
Everywhere you go, there's a big concern for privacy - medical record privacy, photo privacy, gps location privacy, etc. This is no different.