I had a chance meeting yesterday with a young lady in the local neighborhood take-out joint. While waiting for my order she saw me playing with my RedLaser barcode reader on my iPhone. She took hers out too and asked me if mine was jail broken. Mine is pure Apple, so I didn't have anything to really contribute as, she enthusiastically showed my hundreds of her free downloaded applications and a customized interface screen (ATT replaced with her name).
I suppose I'm a bit naive as I never realized the pirate infrastructure was so well formed for the device. Of course, I also did not know that Apple provides tools for jail breaking as noted on GigaOM. Cydia is a GUI for jail broken iPhones and an extensive repository (aka a store) for applications (mostly free). It's incredibly popular with 170,000 people liking it on Facebook
One reason for the popularity is free. The other is a spate of really cool hacks, a top 10 list is noted here.