I don't think that's a meaningful parameter to think about? I'd say that on any social network, I have meaningful, ongoing relationship with maybe 20 people. I suspect that's the norm. But that doesn't mean you can join a social network with 20 users and get that. I mean, if it's a mailing list for friends and family, sure. But not if it's 20 randomly-selected strangers from around the world.
So the critical mass to make the "random stranger" type of a social network work is much, much higher than the number of daily interactions you need to keep coming back.
By the way, if your number is not the same as mine, I am not intimating that this makes you deficient in some way. Everyone has their own number.