On my side, my experience was fairly negative. The technical and scientific discussions were rare, mostly because the conference scope is so large that the probability to chat with people sharing your scientific concerns is low. Actually, I have wondered what I was doing there during three quarters of conference time. Finally, I saw three reasons to attend big academic events:
- awarding scientists: I think that scientists have been excellent students, that their commitment to excellence has again risen once they embrace an academic career, and that they are still not paid accordingly. Scientists do not receive bonuses in cash, however they frequently travel in wonderful places, with great banquet and rooms in palace. Conferencing is an award, which can be typically offered to a worthy PhD student. Similarly, professors do not hesitate to self-award with a full paid one-week conference (grants and funding allow traveling a lot, lets enjoy it). For those who like big hotels and international cities, big conferences are perfect.
- meeting people from your local community: in a crowded amazingly large banquet, people first tend to cluster through languages or institutions. French chat with French, Chinese with Chinese, and members from University X with other members from University X. These "local cluster conversations" are easy to start (what plane did you take, how bad is the food in your hotel, how jetlagged are you, etc.). These local cluster conversations have at least one benefit: you have time to chat with people who you are used to meeting in local events without any chance to really discuss with. Therefore, a meeting in Japan is the place where you enhance your social network with people that live at less than 200 kilometers from your office, which is 10,000 kilometers away from Japan.
- grenouilling during hallway conversations: it seems that the best translation of grenouiller is to plot. In most multi-track conferences, many people prefer to stay in the lobby and do not attend talks. They are not wrong, because many scientific talks are actually bad, and I don't think that a series of talks is the best way to foster scientific conversations. However I am afraid that conversations in the lobby are not worth a trip of thousands of kilometers neither. A large part of conversations I heard or participated was related to research administration: what will be the next event-to-attend, am I in the Program Committee of next big event, what are the latest news about the next national funding call, where could my post-doc find a decent position, if I invite you in my steering committee, would you include me in your steering committee, what are the latest transfers in the academic world, etc.
Probably because I expected some scientific enlightenments from meeting so many smart people, I have been disappointed. In particular, I definitely disagree with the scientists who argue for more maxi conferences. Next month, I will attend Sigcomm, which is a single-track reasonably-crowded (500 people) conference. Lets see if middle-size conferences are worth degrading my carbon footprint.