The referees in the World Cup this year have received a lot of criticism, especially from the ABC/ESPN announcers and supporters of the US team. Some of it is deserved and some is just relocating blame that rightly should be placed on the US team. However, I found this page on ESPN.com that rates the WC referees and, interestingly, the referees the US had are ranked quite low. I don't think there was a conspiracy or anything like that but make of that what you will. Carlos Amarilla, who officiated the USA-Czech Republic game, is tied for 15th out of 22 referees in the WC. Jorge Larrionda--the USA-Italy official--is rated #20, and Markus Merk--the USA-Ghana official--is tied for 18th. It is unclear how these rankings are determined but I assume it is not public opinion.
On the other hand, I have watched every match thus far and must say that the referees have generally performed very well. I tend to agree that the officials have reached for the cards rather quickly to the detriment of the players and games. In some instances the cards are meant to prevent a game from getting too physical that is anticipated to be played that way, but usually I think it has been just antsy refs trying to meet FIFA's demands to the detriment of the games. Larrionda was officiating in this manner in the US-Italy game and the only call I would quibble with was Pope's second yellow, but Pope was playing with fire at this point.
However, there have been some serious blunders this year. Referees do make mistakes and I can't say whether this year has been above average for the WC or not. Here are some the most obvious errors in my mind. Markus Merk awarding the PK in the US-Ghana match; Benito Archundia and his assistants not seeing France's second goal against Korea; Carlos Amarilla in the Tunisia-Ukraine match where he awarded Shevchenko a PK on an obvious flop and missed a clear Ukraine handball in the box for a Tunisia PK (I think this was the worst because it could have cost Tunisia an advancement to the second round); and Graham Poll and his 3-yellows to one player debacle in the Australia-Croatia game.
The officials in today's first knockout games were very good and I expect the officiating won't be as big of an issue from now on. If it is you can go to here to read about an actual soccer referee's view on the performances of the referees. I really recommend this page if you have any interest in a more objective, or at least less impassioned, view of the officials.
Update 6/25/06 2:04 p.m.: I would like to add the list of bad performances by officials Valentin Ivanov, who officiated the Portugal - Netherlands match. He gave out 16 or so yellow cards and 4 red cards (a new record). It wasn't just one or two calls in this match, it was the complete loss of control by the referee from the very outset of the match. Too bad because it could have been a really good game.