Silver has a rich history as an antibiotic/anti-microbial. It just works. Water stored in silver containers stays fresh -- this is why the Roman Empire used them.
Where the controversy and confusion begin is, as usual, in modern times. I can't legally make any medical claim here, but I can say that the claims the medical industry makes about "silver turning you blue" are ridiculous when dosing properly. More info on the Blue Man hoax
Argyria results from prolonged contact with or ingestion of silver salts. Argyria is characterized by gray to gray-black staining of the skin and mucous membranes produced by silver deposition. Silver may be deposited in the skin either from industrial exposure or as a result of medications containing silver salts. 
Prior to 1999, colloidal silver was viewed as a "Pre-1938" drug and not subject to FDA approval.  Since that time, colloidal silver is no longer considered a pre-1938 drug  but can still be marketed as a dietary supplement.
Colloidal Silver by another name... Collargolum
By reason of its colloidal nature collargolum has vigorous catalytic effects which induce or enhance the processes of oxidizing bacterial toxins in the organism This fact was proved by Schedc Hamburger Robin and others Prof Solis Cohen Jour Amer Med Asso Oct 20 1906 stated It is quite probable that the therapeutic value of colloidal silver is largely due to catalytic action in taking up and again yielding thus destroying toxins bacteria or diseased cells a chemical amboceptor action to an illustration made familiar by Ehrlich through such action it may prevent or retard sepsis It certainly has a definite therapeutic action and should be employed more extensively in larger and more frequent doses The Railway Surgical Journal 1907 
Uses / Testimonials
I'd love to collect some more information and even testimonials here. Perhaps you can help.