It seems that even in the age of Internet, most mathematical collaborations are born (and pursued) off-line.
However, I wonder if there exists a "matchmaking website" for mathematical collaboration on specific projects.
However, I wonder if there exists a "matchmaking website" for mathematical collaboration on specific projects. I'm thinking of MathOverflow meets Upwork, which may turn out to be very useful in a variety of circumstances (and indeed, if there is no such website, it could be something worth thinking about).