we found a typical case that generates many support tickets:

some people install they applications on a memory card (especially on
Smartphone where the internal flash memory is more limited).

then someday their phone have problem, so they get a replacement from the
wireless operator, and they try to run all their installed applications from
the memory card.

of course, it does not work well, because those applications were not
installed on the new phone, so any needed registry settings are not there.
but average people don't understand that they should not do that.

the problem is that the OS itself does not complains, it does not prevent
those never-installed applications from running from the SD card, and so it
is the responsability to each application to detect this situation and
display some sort of informative message telling the user:

"You are trying to run an application that was not properly installed on
your phone. even if you install an application on a memory card, the
installation process store some necessary information in the registry (which
resides in your device). if you have a new device, you NEED to re-install
all your applications using your new device."

of course, you could go on and explain people how to do a backup and
restore - if their new device is the same model as the old one, and how to
re-install applications using ActiveSync - if they used setup-files rather
than Over-The-Air CAB files to install their apps.

but i think it's important that all applications that rely on some registry
settings installed at init should detect this situation.