The Momentum Of Failure claims it's totally acceptable to fake a beard (or mustache) if you can't (or don't want to) grow one.
We at Build-A-Beard have one word for that:
LAZY.
I mean, when Nick Cave wanted to man up, he did it for real.
See:
when Nick Cave decided he was tired of not being awesome**?
He didn't go half-assed.
Now even his Glamour Shots will fucking kill you.
Yeah. Grow a real beard or shut up, that's what Tim Harrington says.
**note: we here at Build-A-Beard do, in fact, acknowledge that Nick Cave has never been anything less than awesome. His new molester 'stache just makes him moreso.