Version:           unspecified (using KDE 4.5.3) 
OS:                Linux

Should be useful if panels can be independent for each activity of your system.

Depending of the activity you should need some specific elements that other activities will not need, for example these scenarios: 
- I could have a default activity that I could have the default panel and icons of applications like Kickoff, Dolphin, Firefox and notification widgets and digital clock...
- An activity for development could have different icons related to programing or additional panels with useful widgets... 
- An activity can be done for netbooks with the same widget additions in the panel (and placed in the same place) like when plasma is set in netbook mode... 
- An activity can be a multimedia desktop that use 1 or 2 vertical panels (one per vertical edge) with widgets related to multimedia stuff. Or no panels and all widgets placed in the desktop, to be used in a TV screen as a multimedia station... 
- A gamer activity can be simply the standard panel and additional panels with auto-hide mode enabled and all your most used games icons in these panels...

Currently these scenarios are impossible because you are forced to share the same panel/s on all the activities you add.

Reproducible: Didn't try