Regardless of what operating system you use, logging in and performing normal (non-administrative) tasks with administrative privileges is a dangerous practice. Unwittingly executing a program concealing a Trojan horse as an administrator will provide administrative rights to that program, and the impact may be much greater.
Although increased security generally causes increased inconvenience, the runas command provides a convenient means of running a program with different credentials, typically as administrator, while working as a less privileged user.
