There are two aspects to this question. One is whether there are large numbers of teens having oral sex instead of intercourse and the other is whether (if there are) this is a bad thing.
As to the first, I believe that this is an issue that has been over-hyped. Someone like Oprah Winfrey gets the idea that all teens are having casual oral sex and suddenly it becomes conventional wisdom that this is true. As this link shows, 16% of teens have had oral sex but not intercourse. This does not seem to me like a crisis.
Of course, my attitude towards this is colored by my attitude towards the second aspect of the issue. Is that 16% too high of a number? It would probably be better if it were lower and teens were not having intercourse either. But would we really prefer that those 16% should have intercourse instead? Doesn't seem likely.
So, I think that the prevalence of oral sex has been overstated by the popular media and I think that the amount of such behavior that is going on is not a serious cause for national concern.