Actually it's different carrier's system not different frequencies. If that were true then you could use a phone purchased for AT&T on T-Mobile and you'd get 3G on both. That doesn't happen because they both use diferent frequencies for their 3G while using the same technology (GSM).Just means it will support different carriers frequency
Free even.Yes you can as soon as they're available. I bought my factory unlocked 3Gs in Germany on one of my flights over there. Now I just worry about JB for the apps and if a JB comes out without the possibility of an unlock I don't worry about it. The reason people buy them here locked is easy.
1- they don't travel overseas much
2- you can get them subsidized by the carrier so you get a $700 phone for $99
http://mobilesyrup.com/2011/10/07/future-shop-1-day-sale-iphone-4-16gb-free-on-3-year/A 4S free? Show me where.