Let's not compare condoms to Plan B.
Anyone who has used a condom will know its limitations. To be honest, I hate condoms! (This may explain why I have 3 kids!)

The reason why most folks don't use them is because they take away a lot from sex. The feel is just not there...no matter how much Trojan wants you to believe the opposite. They dry up and crack...thus, limited "shelf life." They are not cheap. Although condoms are an excellent tool to have, it is quite obvious why it has not achieved its societal goals of limiting unplanned pregnancies and STDs. Why? They ONLY work IF you actually USE THEM.
Plan B is different. You can quote me data saying how condoms did not lead to more sex etc.. And I will tell you that Plan B will be different. For most teens, the WORST THING that can happen to them is pregnancy. Agree? No, they don't think about STDs, esp. in the heat of the moment with tons of peer pressure. Pregnancy is on everyone's mind. It is the ONE thing that she cannot hide from her parents...and is legally binding to the male partner. What does Plan B provide? It gives teens a "have cake AND eat it too" mentality...something that condoms could NEVER provide. It allows them to have splendid intimate sex with all the pleasure of such activity...without the one main consequence that is an absolute killjoy within 12 weeks of sex...vomiting and testing positive for pregnancy.
Plan B is THE Holy Grail for teens. Time will tell if I am right. And I am always right.