> But it's also that the bidding model is a poor way to allocate the money. I don't want the word "insurance" to randomly trigger a $50 ad slot. It's okay if there's some influence from ad slot prices onto how the money gets allocated, but the main influence should be how much I use each site.

Using the normal bidding process was a clever shortcut to get Contributor working as a 20% project, with minimal manpower. Seriously, it was just two guys at first.

It's not currently just two guys. I'll let you read that how you will.