While Apple technically calls it "iPhone IMEI database whitelisting," it's better known around the web as a factory unlock--a process that allows your iPhone to be used on any carrier's network. Unlike a jailbreak unlock, a factory unlock stays with the phone even if you upgrade iOS, wipe the phone, etc. It saves you from the hassles associated with jailbreaking. Apple makes it clear that your mobile phone carrier is the only one that can officially unlock your iPhone. Therefore, sites offering third-party iphone unlock services are fraudulent "businesses" by definition. Like any black market, the risk of getting scammed is beyond sky high--it's virtually guaranteed. Here are some thoughts if you are pondering the dark path of rogue unlock services.
Check Apple's carrier list.
Apple has a list of all iPhone providers along with their unlocking policy: http://support.apple.com/kb/ht1937 Does your carrier do unlocking? If so, then ask them directly how to get your iphone unlocked. If your carrier doesn't unlock iphones, then I recommend giving up now. For example, despite recent government regulations encouraging the contrary, the big 3 Japanese providers (Au, Docomo, and Softbank) all maintain a strict policy against unlocking the iphone, even after all contractual obligations are met. Game over, man. Any third-party unlocking site that claims they can unlock such a provider's iphone is a scam. You have been warned.
Do a background check on the vendor.
If you still wish to proceed down the shadowy road through the valley of iphone unlock darkness (Don't do it!), then perhaps it would be prudent to first run some background checks on the unlock vendor you're considering doing business with. I wrote a more general article on how to run a background check on an online business: How to Spot a Fraudulent Online Business
Life's too short. Buy an unlocked iPhone from Apple.
I got burned the first and only time I tried to buy a third-party iphone unlock. Was I merely unlucky, or is that the nature of the beast? Either way, I deeply regret not having walked a more righteous path. Is using a shady unlock service really worth the risk? True, you may save some money; but you may also lose that money and/or find yourself loaded with the time-consuming hassles associated with credit card fraud. Having dealt with it myself, I wish I had just bought an unlocked phone from Apple from the start. If your Apple store doesn't sell unlocked iphones, which used to be the case in Japan, then a vendor like Expansys may be able to assist you. Then you can sell the locked phone using an auction site, recovering some of the money you just spent on that expensive new unlocked one.