It's about ads. The great thing about putting videos on YouTube is that Google does the work of selling ad slots for you, the not-so-great thing is that because those advertisers are actually Google's customers, if they think they might be upset to see their ad running in your video, they'll err on the side of pulling it.
But I daresay if Russell Brand had advertisers working with him directly, most of them would also be suspending their relationships with him right now; nobody wants anything to do with this sort of allegation.