In-person interactions should, in nearly all cases, be valued more highly than internet-mediated interactions. Martial arts are no exception; in fact, they are a paragon example of the vast superiority of in-person communication.
I found the "Throwdowns" of bullshido.org to be the most valuable aspect of that martial arts website. Discussing things online is great, but when you meet physically, a whole bevy of better options arise:
- Trading technique with drastically reduced opportunity for miscommunication
- There is a great release of tension and building of camaraderie by sparring with people using our bodies instead of our words
- Putting a face to a name has been proven to make people nicer
I suggest piggybacking on an existing open mat in NYC so that nobody gets screwed if there's poor turnout.