Well, let's see what the doctors have to say:

Oral sex is considered a low-risk sexual activity. The chances of contracting HIV from it are considered "very, very, very, very, very low" (Dr. Jeffrey Klausner, Director of San Francisco's STD Prevention Unit). However, "other STDs, like syphilis, gonorrhea, chlamydia and herpes, are definitely transmitted through oral sex" (Dr. Jeffrey Klausner).

TIP: Doctors suggest not brushing your teeth at least an hour before engaging in oral sex. Brushing your teeth creates micro-cuts in your gums, which COULD increase the risk of transmission of STDs.
Also, I'm in a 7 year monogomous relationship. If they polled people like me and my partner about condom use, we'd also skew their numbers. Wonder if they factored that in?