Why is it horrendous? The string is concise, unambiguous, and works when you put it in the location bar. Including the scheme makes sense only when there is a risk of ambiguity, and even Tim Berners-Lee admits that exposing such a technical detail to users wasn't the best design decision.

I believe he said horrendous since there is a certain trend that Facebook will, in some sense, be a closed internet. There may come a time when not being a Facebook user means that you cannot see some significant portion of the Web.

Well for facebook.com/productname that means a commercial decision - is it worth excluding a (probably) significant portion of the internet from viewing our product's site.

Why exclusion? FB Pages are public by default, no login required. Some individuals' comments may be invisible due to their privacy settings, but technically non-members are not excluded per se.

Just in response to the parent poster stating that Facebook could become a closed internet, requiring an FB login to access content.

Concise? The superfluous inclusion of "facebook" and the slash negates your claim here.

Or try AOL keyword "productname"!

I think this is great. I don't even have to be near a computer to know I have no interest in the product.