Let's be honest, I spend a lot of time at conferences. Over the past 2 years or so I've averaged more than one speaking engagement at a conference per month, including a half-dozen keynotes. I've also helped organize several conferences, mostly DrupalCamps and DrupalCons. I'd estimate conferences make up more than a third of my professional activity. (Incidentally, if someone can tell me how the hell that happened I'd love to hear it; I'm still confused by it.)
As a result I've gotten to see a wide variety of conference setups, plans, crazy ideas, and crazy wonderful ideas. There are many wonderful things that conference organizers do, or do differently, and of course plenty of things that they screw up.
I want to take this opportunity to share some of that experience with the organizers of various conferences together, rather than in one-off feedback forms that only one conference will see. To be clear, while I definitely think there are areas that many conferences could improve I don't want anyone to take this letter as a slam on conference organizers. These are people who put in way more time than you think, often without being paid to do so, out of a love for the community, for learning and sharing, and for you. Whatever else you may think about a conference or this list, the next time you're at a conference take a moment to find one of the organizers and give them a huge hug and/or firm handshake (as is their preference) and say thank you for all the work that they do.