I was thinking of unlocking my ST17i's bootloader but I saw on the Sony Mobile website that unlocking the bootloader will result to the deletion of DRM keys from my phone. What exactly are they? And what will be affected if I lose the said "DRM keys"?
DRM stands for "Digital Rights Management", and mainly is used with sold eBooks/PDFs and the like (and also for sold music files plus maybe even videos). Those keys are to identify your ID as to prove if you have permission to access those documents. If you never bought any of those "crippled" documents, chances are you don't have to bother.