I don't know anyone that has had this surgery.
Without presuming to know why you are asking...all I can say is that it
seems incredibly risky for such a sensitive and delicate organ.
Are you talking about the sort of implants that allow impotent men to have erections (as i think neversickanymore is referring to)?
Or is it a size thing?
If it is the latter, I'd recommend watching
this documentary.
Frankly i don't know much about the topic, besides what this film explores - but it is a fairly interesting investigation of western attitudes towards male sexuality, body acceptance, ideas of what is "normal" and the inadequacy some men feel in terms of their anatomy.
The conclusions drawn regarding surgery are quite negative, but it is approached with an open mind. An interesting film, regardless of its relevance to the viewer.