In Saturday's Cup Final Chelsea's Florent Malouda let go a shot that hit the bar, bounced down over the line and then back into play. Neither the ref nor the other officials thought it was a goal and so they carried on. TV replays showed that it was a goal but thankfully it wasn't controversial. Chelsea held on to their lead and won the cup. This gave rise to the usual arguments about "modern technology". (Football people's belief in "modern technology" is about as well-grounded as 17th century villagers' belief in witchcraft.)
It works in cricket and rugby, they say. Well, in those sports it works far from perfectly and both games have one characteristic that football doesn't. When a decision needs to be made in cricket and rugby the ball is dead. In the Malouda case play was continuous and the only person who can stop play is the ref, who saw nothing wrong with it. So who would stop the FA Cup Final so that a TV replay could be consulted? Guus Hiddink? Roman Abramovich? One of the players? A representative of a Chinese gambling syndicate?
The technology may well work but somebody has to provide the interval for it to do that work. If you allow anyone other than the ref to be the arbiter of all decisions about how play is conducted you're letting in all manner of madness.