The only problem I have with the morning after pill (Plan B) is that many people use it as a birth control method instead of the usual precautions, and since it's a massive dose of hormones it can mess up a woman's natural balance. Of course, it also provides no protection against STIs.
I do support its use for occasions when it's necessary. I know several SPs who keepat around for when there's a problem with the condom, or when a customer manages to slip a condom off and go BB and it's the fertile time of the month (which is only a 2-3 day window). Some SPs think the morning after pill works against STDs, though, and that's just dangerous thinking.