biology lesson: regardless, the risk of acquiring most forms of STD via oral transmission is relatively low -- tho you can transmit cold sores (herpes simplex 1) to the genitals, and genital herpes (herpes simplex 2) to the mouth, and transmission of gonorrhea, hepatitis B, syphilis, or chlamydia is also possible. herpes is visible in it's infectious stage...great excuse for lights on. hepatitis B vaccines exist, so go get yours done. syphilis, chlamydia, and gonorrhea are curable by antibiotics. all studies show HIV transmission to be a very low risk for oral transmission.
I agree with many of these points. It is possible to get STDs from oral sex, but the odds of getting most types of STDs from oral sex are small. It is also possible to get some diseases from kissing such as HSV-1 and mono. I highly doubt that prevents people from kissing.