At least in CS theory, I don't see any crucial importance. These days it's easy to follow the latest developments online. If you're interested in someone's work, you just email them and start a collaboration. Sooner or later networking in hallways may become a thing of the past.— Mahdi Cheraghchi (@cheraghchi) March 6, 2020
I don't disagree with anything Mahdi says except for the "crucial importance". Great ideas come from chance encounters and random conversations. Many of my research papers would never have happened if not for a conversation had at a conference or on the plane or train rides that took me there. Harken Gilles Brassard's origin story of quantum cryptography.
One fine afternoon in late October 1979, I was swimming at the beach of a posh hotel in San Juan, Puerto Rico. Imagine my surprise when this complete stranger swims up to me and starts telling me, without apparent provocation on my part, about Wiesner’s quantum banknotes! This was probably the most bizarre, and certainly the most magical, moment in my professional life6. Within hours, we had found ways to mesh Wiesner’s coding scheme with some of the then-new concepts of public-key cryptography.... The ideas that Bennett and I tossed around on the beach that day resulted in the first paper ever published on quantum cryptography, indeed the paper in which the term “Quantum Cryptography” was coined.And Footnote 6 read as follows.
At the risk of taking some of the magic away, I must confess that it was not by accident that Bennett and I were swimming at the same beach in Puerto Rico. We were both there for the 20th Annual IEEE Symposium on the Foundations of Computer Science. Bennett approached me because I was scheduled to give a talk on relativized cryptography on the last day of the Symposium and he thought I might be interested in Wiesner’s ideas. By an amazing coincidence, on my way to San Juan, I had read Martin Gardner’s account of Bennett’s report on Chaitin’s Omega, which had just appeared in the November 1979 “Mathematical Games” column of Scientific American—so, I knew the name but I could not recognize Bennett in that swimmer because I did not know what he looked like.After we see a slate of conferences held virtually due to the virus, networking may indeed become a thing of the past. But we'll never know the research not done because of people who never connected.