I’ve made my Blackberry Bold SIM-unlocked, because the Blackberry I bought in Japan was locked to NTT DoCoMo, a Japanese mobile phone carrier, so when I was abroad I had to fear the phone bill charging highly expensive roaming prices.
Unlocking was easy: I got an unlock code for my device at http://expressunlockcode.com/bbexpress.aspx by paying $19.99 and giving the IMEI for my device, phone model, carrier name locked to and my country to the unlock code provider. Several hours later from paying I got an unlock code for the IMEI I gave. Then I unlocked it by following the instructions at http://www.mobileslate.com/blog/2008/11/14/how-to-unlock-rim-blackberry-9000-bold/. Once unlocked, you can use not only NTT DoCoMo’s SIM card but Softbank’s, as shown in the above picture.
(Blackberry services aren’t available with Softbank’s SIM card, though)