No, when a can of fruit is dented, the worry is that the thin protective layer on the inside of it has become damaged, allowing the contents to spoil. Kegs aren't coated, so they're fine, they just look bad. Unless there is major damage to the inside with scratches or creases which could harbor bacteria.
Small dents are of little concern in a corney keg so long as it still holds pressure. However, that 'little' concern' comes with a series of things to look for.
If a dent is too close to a seam that it comprmises it, even if it still holds pressure, it can create a ridge or crack where infectous agents can hide.