Bah. The
American Dental Assocation really annoys me because they lie about this stuff to the point where even dentists who don't necessarily encourage it admit the ADA is wrong. Oral piercings heal just like any other part of your body.
Infection is only a threat if you're stupid and forget your
mouth wash or start
French kissing people a week after getting it. After a month or so for
tongue piercings and various time periods for other oral piercings, it's fine. And as for swallowing jewelry, proper
body jewelry will not come apart. Even if somehow you do swallow something, you'll be fine.
Inhale it and you're in trouble, but that's true for anything you put in your mouth.
That said, oral piercings do pose a health risk. Labrets can mess up your gums and lead to tooth loss if you're not careful, but that's easy to avoid with proper jewelry. Tongue piercings can do the same if you have bad placement and jewelry, but that's really rare. The larger problem with tongue piercings is tooth damage - bite down on your barbell and you can crack a molar. You can also chip your teeth. Make sure you go to a good piercer if you get your tongue pierced so they can place it properly and give you the correct size jewelry. If you're responsible, there's no real risk in oral piercings.
Heh, two other dangers of oral piercings I found out recently - lousy kissers will make your tongue hurt, and it's hard to blow bubbles with bubblegum. Ah well. The prices we must pay.