I ran a similar site a few years back (youtipit). The biggest challenge was actually getting people to give money for things they can have for free. Looking at Chads figures, I think there definitely has been a huge change in the way people respect "free" work, and are now a lot more willing to pay for it.

I hope for him (and all others in this market) that this trend continues and that more people can start making a living from free work.