How can a shirtless Justin Bieber test the performance and scalability of your servers? Witness a shirtless Biebs engaging his fans online during the Grammys. He tweets his intent to talk live on Livestream. Magnified by retweets from Beliebers, the traffic to Livestream crushes their service.
JB then jumps to Ustream with the same disappointing results. Dejected, Justin has to post stuff in a non-live venue to appease his fans. So the best stress test for your systems is actually this.
Though I don’t think any amount of scalability can withstand the onslaught of traffic to see Justin Bieber’s next tattoo.