It seems like the FB founder has nothing but positive things to say about blockchain technology.
There are rumours going around that he will release a cryptocurrency for use on WhatsApp, but given the privacy and censorship concerns over FB, I can't see many people going for it.
He is a latecomer but still a good development for the crypto community, he should be very big names in a financial and social network have voiced out their support, he does not want to be the only one left in the field.