The software must run via .exe or .app files directly from removable media. It should not write to the Windows Registry or require admin passwords.
The "Portable" aspect is the defining characteristic of this era. Connectivity is no longer tethered to a desktop in a family room. It is in the pocket, at the dinner table, and under the pillow. This portability has dissolved the boundaries between private thought and public performance. The Paradox of Portable Identity teen mega world net portable