Spontaneous, arising from situations, is way better. I wouldn't, or wouldn't ever, have tried to organize one through the internet. It just screams of disappointment. Try finding situations where it might arise organically. Don't push it.
I know someone who successfully organized one though, but it was a long time ago when the internet was new.
I think a lot of things online have become spammed and polluted in time. Even my ex-wife recently returned to a dating site she successfully used circa 2007 and 2008, only to find it full of bogus accounts. It had become a waste of time. She met one guy from it in her recent dating.