What are the advantages of angling your saddle down? I have seen a few people do this where their saddle was angled down a bit. Why would someone do that?
In general, I don't know why one would do this. Especially men.

Here's what Sheldon Brown has to say, and I tend to agree:
"If the saddle is tilted down in front, the rider will tend to slide forward onto the narrower part of the saddle. Women who are riding on saddles that were designed for men frequently tilt their saddles down. This will relieve some of the discomfort from the saddle itself, but creates new problems: The downward slope of the saddle causes the rider to tend to slide forward, and this can only be counteracted by pressure on the hands. Thus, poorly-angled saddles often are the cause of wrist, shoulder and neck problems, due to carrying too much of the rider's weight on the hands."

Lennard Zinn mentions that a "very slight" tilt in either direction may be optimal for some riders; but no more than ~2 degrees. Basically the same reasons that Sheldon Brown mentions. The downward forward tilt adds pressure on the arms, back, and shoulders due to sliding forward. 

You want your "sit bones" to be on the widest part of the saddle. If you slide forward, the pressure will shift from the sit bones to the perineum; and that's probably a bad thing. There are special cases for tilting the saddle nose downward; but for the general rider it's not necessary.