Loss of Hearing
Loss of hearing from ear piercing is an urban legend — under normal circumstances there is no way for your hearing to be damaged by a piercing. Sure, if a piercer slips, falls, and rams a needle through your eardrum, then you could have hearing loss, but that's just not going to happen.
As far as an infection traveling inward and doing such damage, but it's one of those "one in a million" things; you're just as likely to lose your hearing from scratching your ear and having a cut from your fingernail get infected and travel inward.
Large gauge inner conch piercings and other piercings that noticeably alter the structure of the ear will however make slight differences in the ability of your ear to channel sound (like a funnel) into the inner ear. The degree of this change should be extremely minor in normal circumstances and I doubt most people are even aware of it.
