Yeah, why not? The only problem I can see with all men taking it is that:
a) if a woman gets pregnant (out of marraige), she's stuck with the kid anyway, however he really has no reason to worry about conception occuring. Although with DNA testing, "I'm not it's father" will be vanishing from the english language
b) Some men are wimps and cant stand the feel of a prick in the side of their arm, yet would gladly get into a bar brawl. I don't understand this group of people, but they do exist and confuse the hell outta me.
c) Men are lazy, or scared that it will cause perminant damage to them or their ability to produce sperm, or make them less masculine.
Once again I believe the male ego will prevent most except the married men to go along with this.