At my newspaper, Público, we created a daily podcast called P24, which features journalists and guests discussing the news of the day. P24 was initially sponsored by Google and was such a success that when the Google funding came to an end, Público decided to keep the project going. Not only that, but it launched several other (non-funded) podcasts, created by the politics, world, and sportsdesks.
If you are going to take money from sources that could be considered tainted — and Google and Facebook very much fall into that category, given that they are the very powers we should be holding to account — then this is very much the way to do it.
Use their funding to launch something, but plan from day one for a path towards making it sustainable without the sponsor. Equally use their money to experiment without significant financial risk to your own organisation.
I'd love to say "turn down Google and Facebook money", but that's not realistic in the age we're in. So, the discussion has to be "how to use their money ethically".
This is a concept that Público are clearly on top of:
One issue that arose in connection with the sponsored projects was the need for transparency about the nature of the relationship between media outlet and sponsor. To keep the trust of our readers, we have to be absolutely open about which content receives financial support and who the funders are. We also need to help readers understand the difference between sponsored content in which the sponsor has a say, and the sponsoring of projects where the journalists retain full editorial independence.