Benefit of "Run as" self

[mmonaco27]

How exactly does running a program as the current user help anything? I really don't see what security benefit it could/should provide.

[gerbil]

"Run as" is a sandbox [the top button...], a virtual environment windows creates to run the pgm. It allows the pgm to do as you wish it to data files, but will not permit it to change registry entries, or modify the OS.
Think of Run as as a new user, but with different, more restricted privileges.
Of course, you can use Run as to start an admin account [the bottom button...] so you can do normally restricted stuff if you are currently logged on as a user with no admin privileges. Provided you know any logon and password required. Not a sandbox, in this case.
But if you use Run as as a sandbox to run something that is actually infected, your AV should jump out at you with a warning. And break it.