Sports fans attending the London Olympics have been told to avoid sending non-urgent text messages and tweets during events because overloading of telecommunications networks is affecting television coverage.
Coverage of the men's road cycling race on Saturday left many viewers in the dark at times, Reuters reports.
Commentators on Saturday's men's cycling road race were unable to tell viewers how far the leaders were ahead of the chasing pack because data could not get through from the GPS satellite navigation system travelling with the cyclists.
It was particularly annoying for British viewers, who had tuned in hoping to see a medal for sprint king Mark Cavendish.
Many inadvertently made matters worse by venting their anger on Twitter at the lack of information.
An International Olympic Committee (IOC) spokesman said the network problem had been caused by the messages sent by hundreds of thousands of fans cheering on the British team.
"Of course, if you want to send something, we are not going to say 'Don't, you can't do it', and we would certainly never prevent people," he said. "It's just - if it's not an urgent, urgent one, please kind of take it easy."
An explosion in the use of mobile phones to access the Internet and take and send photos and video has made London 2012 the first true "social media Games", but also put pressure on the networks. The host broadcaster, the BBC, is enabling fans to see many events live on their smartphones.
O2, subcontracted by BT to provide mobile services within the Olympic Village, suffered a glitch this month when a third of its customers were hit by a 24-hour network failure.
Steven Hartley at Ovum Telecoms Strategy said at the time that, while mobile capacity was being upgraded at transport and crowd hotspots, spikes in demand at peripheral sites could prove disastrous.