I'm not saying it's a good solution, im saying it's a compromise - and a widely acceptable one given the abundance of devices that employ such a system. The fact is most people will make such compromises for the added security.

Copy and Paste is a separate issue completely unrelated to the sandboxing of applications - i just threw it out there as an easy mechanism for approaching the problem - though it is available in almost all platforms that do such sandboxing sans WP7 which gets it by the second week of March 2011, of course this would be well before any Nokia WP7 devices will even be announced.