Just upgraded to Lion (mid-2008 C2D 4GB RAM) and can't get the Guest Account feature to work as advertised. It's one of the things I was most excited about, as my wife's friends and family are often asking to borrow the computer when visiting. Next thing I know, Amazon is showing me jewelry under its "More Items to Consider" section and vampire romance under "New For You."
I enabled Guest Accounts in System Preferences and used Parental Controls, I thought to lock things down. I just want guests to be able to use Safari or Chrome, Pages & Numbers, Text Edit, iCal and a few other basics. I specifically didn't want them in iLife or the App Store, etc.
No matter what settings I choose in Parental Controls, all those apps are in the Dock.
Additionally, every time a Guest Account opens, I get immediate error dialogues about "You don't have permission to open..." and it's one of the apps I wanted to restrict access to.
Maybe the above behavior is the way it's supposed to work. If so, it seems stupid... Not elegant. I'm surprised, but certainly not delighted.