I think the reason it hasn't been implemented thus far is because the sheer size of football (soccer) field would make it cumbersome to have the roving cameras suspended on lines like they do in American football. However, I've been wrong many times before and the true reason could still be speculative at best.

More officals is a must. France got in to the World Cup 2010 FIFA because of a hand goal. That is a cheat.

They have like 5 ground cameras, and 2 sky cameras.
Also, I watch the games, and their is never a point where the ball controller is out of view.

Also, last time, the zidane headbutt, that wasn't even near the ball, but they still had closups in like 4 angles.

TV replays aren't the same as the video feeds refs get, cula, plus at the resolution they were using they probably just cut out the sides and zoomed up the video. It's not a very effective system, and something more like the American football version of refereeing would be much better.

The amount of disallowed goals this world cup has been ridiculous.

Well, do you know this?
Do they have special shit cameras for ref viewing?
Because in American sports TV feeds are what the ref sees.

Having a separate official with a little T.V. screen (or something like that anyway) that can confer with the referee about disallowed goals is something that needs to be implemented in football matches where a lot is at stake. It wouldn't take long and it would improve the game drastically.
Having it like the system they have in tennis grand slams like Wimbledon and the Australian/American Open would also be good so it would be up to the players, or the teams captain, to get a definite full proof decision on whether a goal was in or not. + they would only have a couple of chances to do it.
I don't think they should use it for anything other than dis/allowed goals though, otherwise things would stop and start too often.

A tribunal kind of thing (like in AFL (Australian Football League (Worst sport ever made))) wouldn't be bad either. A committee of some sort that could look back over the games and point out blatantly obvious dives and then give out some hefty fines or match bans for the people who dive. Because the only thing that sucks about football is the people who dive, in my opinion.

Well, think of it more as any difficult or questionable calls are reviewed.

That wouldn't slow play down too much, and good refs could be discerned more easily, and kept in check.

Totally agree, some of the stuff the refs let go is terrible.