The problem came to a head at last year's festival.

"There was just an insane number of iPhones up here," said Justin Simmons, associate director of IT for the nonprofit Sundance Institute, which puts on the festival.

Users of all types of smartphones ran into a wall when they tried to do something as simple as making a call or checking their e-mail. Even worse for Sundance, visitors often couldn't use the festival iPhone app they had bought for $4.99, which included data-hungry features such as movie trailers, Simmons said. Cellular data coverage, from all service providers, just wasn't cutting it. Simmons and his team didn't have to endure any tirades by spoiled movie stars, but complaints did come in from many people in the film industry and the media, he said.

So for the 2011 festival, Sundance will be expanding its free, public Wi-Fi network from the handful of locations offered in the past few years to 12 indoor and outdoor venues. Ruckus Wireless, a Wi-Fi specialist in Sunnyvale, California, donated equipment and services for the infrastructure.

The expanded network should offer a better visitor experience while also taking pressure off cellular networks that need to carry voice calls, Simmons said. Organizers think the free Wi-Fi will be necessary even though AT&T plans to triple the capacity of its network in the town and also bring in three "cell on wheels" trucks, he said.