Many phones shipped with bands locked out like if AT&T only uses 850 in the states then 1900 would be completely locked. In addition 850 is probably limited to the NCC 410 which is AT&T. You have to unlock one or both in almost all American phones to use them on another network or in another country. Europe USUALLY has 900 and 1800 unlocked but providers there still sometimes lock the NCC so you can only use it on their network. There is also the BRL on the sim card that will limit what networks you can roam on no matter what is unlocked on the phone.

No the guy is just completely wrong and some clueless guy with moderator points upvoted him

This is also completely not true. This is "unlocking" your phone and has nothing to do with changing your IMEI/MEID. I can use my verizon LTE android phone in South Korea. I just have to unlock the GSM bands and put in a relevant sim card. You can find instructions to that effect here: http://forum.xda-developers.com/showthread.php?p=29010852 again please don't spread completely false information. Google exists. use it.

this is completely false. Don't spread bad info. Google "how to reprogram your IMEI" I'm not sure the legality of posting a link to this kind of stuff. Please educate yourself before making false blanket statements.

It's extremely easy to reprogram the IMEIs or MEIDs. Anyone who can install a copy of windows can manage it with some of the readily available free software floating about for "research purposes"

That's because the post 9/11 "let's share everything" mentality that was mandated by SECDEF.

Of course they blame it on computer utilites! Otherwise they'd have to start trying to catch clever timetraveling bandits!