I think you'll get a lot fewer people participating when they have to put the money in themselves though. I know I wouldn't. It's not that I don't want to see Bitcoin expand, it's that I don't want to be at a net loss for doing so. And I think a lot of other people are as... stingy... as I am in that regard.
If it can be done for free, there will be a lot more people participating.
How about a combination of both? You can enter in a serial number, fund it yourself, and release it into the wild or you can enter it and wait for the site admin to fund it.