Are you concerned that every employer would begin do follow these practices and require auditions? How likely do you think that is?
I'm not saying "don't do it." I'm saying that from my perspective, I think it's a flawed interviewing technique and it's not something I would be interested in when applying for a job.
If it works for you, then by all means go for it. I'm just saying it doesn't work for me.
[1] http://www.joelonsoftware.com/articles/fog0000000073.html grep for "no hire" just to get a feel
Trello and StackOverflow are so much nicer now than FogBugz was then so I guess he hired better people. But I think a lot of his advice became vogue more because he was an entertaining writer than a great software entrepreneur.