I know Stef has talked about this quite, and I believe he has good reasons for a 100% donation-based model. However, I still believe that the best way to grow the show is to simply enable ads on YouTube and thus I will bring this up once again.
FDR is forecast to have 52.5 million views over the next year. This translates into $75-179k in YouTube revenue (http://youtubemoney.co/).
Stef does not have to actively promote any product or service, and there will be no interruptions during videos like Stef has mentioned before as a reason to not use advertising. All that would happen is that some videos have short ads that can be skipped at the beginning, and there will be small pop ups on videos. This is extremely widespread on YouTube and widely accepted so I don't think people will find it to be a big nuisance. Any lost traffic from these minor nuisances would be more than offset by the increased reach FDR could have from an additional $100k/year put into growing the show. Stef could hire an additional person or two, could advertise his show elsewhere, or any number of things with this additional revenue.
So, I'd love to hear some good rationale for why this massive revenue stream should continue to ignored year after year. I completely understand why Stef wouldn't want to do "live reads" for sponsors or anything like that, but this is extremely passive advertising with which Stef does not have to be affiliated with.
Other sources for calculating YouTube revenue:
http://socialblade.com/youtube/user/stefbot
http://www.investopedia.com/articles/personal-finance/032615/how-youtube-ad-revenue-works.asp