Well it isn't going to be the entire network power, cause that will be to difficult to organise. However 30 PC helping someone rendering for bitcoins is  good enough, It definitely better then weating 3 weeks or to go to big company's who ask a lot of money to do it.

Edit: They also make the difficulty higher to make sure that It can still be bizy but now you can still mine. It is also for the end game of this network. We need more money for bitcoins comming in and money that want to use the networks power is good.

We might even start a company that renders files with bitcoin. Just to let the graphic art people also see some benefits in this.