I know you used to be able to paypal $1 and message anyone on facebook. I would not take anything seriously on facebook twitter or instagram, they are all basically a pit of nonsense and BS.
The only thing I would use facebook for is to snoop in to see if you know someone from high school or someone you just dealt with, out of curiosity. Posting on facebook is less personal than even texting, it is a complete F-ing joke.
I would not even bother messaging girls on facebook, i would at least sign up to an online dating site, that, as far as online goes, would be more of an actual attempt.
Women blocking you on facebook or a dating site sucks but i would say it is very common. For me to meet 1 woman on a dating site, i might have to message 100 women and then in the process get blocked by 5 or 10. Women have so many messages per day that if they don't block a lot of them you know