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Below are some of the top and Biggest Facebook Groups for crypto currency and bitcoin.
Links with number of members are as follows
No 1 https://www.facebook.com/groups/ohyaaaa/
Name Bitcon & cryptocurrency
556,015
MEMBERS
No 2 https://www.facebook.com/groups/goodpeopleofthe/
Bitcoin & ICO'S
556,015
MEMBERS
No 3 https://web.facebook.com/groups/1539123079445874/
Bitcoin & cryptocurrencies
419,290 Members