DooMLoRD over at xda-developers has created the Xperia 2011 Easy Rooting Toolkit that allows users to root their device even if they haven’t unlocked the bootloader. The program takes advantage of the zergRush binary root exploit created by Revolutionary.
You have been able to gain root without unlocking the bootloader in the past, but this method only worked for a short period. The ‘Easy Rooting Toolkit’ involves downloading a file, extracting it using WinRAR and then clicking on ‘RUNME.bat’. You then just follow the instructions on screen, easy peasy. Sounds like a wonderful solution for those unwilling to unlock the bootloader. It should also work on all 2011 Xperia devices. Click here for the full details.