Nope. It's not there. The guys that took the phone apart as soon as it was released have put that myth to bed. All of Cingular/At&t's sim cards say 3G on them now and they put them in all their phones even if they are only capable of GPRS speeds.
theres nothing that confirms otherwise.... why would you assume a 3g chipset is installed in the phone when Apple has already announced in first quarter 2008 a 3g ver 2.0 of the iPhone will release.
btw the sim card is a normal att 64k simcard , i activate them in edge phones multiple times a day , there is nothing special about it. only thing that makes it work in iPhones when others don't is the encoding AT&T puts on it during the sim acto process.
People here have no clue what they are talking about...
all of the important components in the iPhone are Apple branded and thus no one thus far has been able to identify all of the chips that are in use. It's very possible and very likely that it has 3G in it. Would Apple really make a whole different iPhone for europe?