After running 7 barcamp networks (2 in LA, 5 in SD) I’ve learned a ton:

• ‘end user’ or ‘home’ wifi gear doesnt work. No matter how awesome you think it is. It just never ever cuts it.
• 2.4ghz is the devil
• you need at LEAST 5-10 megabits of connectivity, preferably with the ability to burst up higher.
• OpenDNS = fail
• Spend the extra money/time/etc and get mesh wireless from a reputable vendor (cisco/aruba/xirrus etc). It will make your life way way easier.

I’ve banged out a quick writeup on the BarCamp San Diego 5 wifi network over on thaumatocracy.com – so if you’re a wifidork or have any interest in how the network was run, pop on by!