Lemierre's syndrome (also known as Lemierre's disease, necrobacillosis or post-anginal sepsis) is an extremely rare disease which has tentatively been linked as a having tongue piercing as a potential trigger. As of mid-2002, there has been a single case, which was that of a 15-year-old boy in San Diego. That said, it is important to note that a single small infection in a piercing can travel inward and become much more serious. (Of course, the same thing can and does happen from paper cuts and even biting your lip).
Lemierre's consists of an oropharyngeal infection (an infection between the soft palate and the epiglottis, the part of your mouth that closes off your throat during swallowing) with anaerobic septicemia (essentially blood poisoning), followed by suppurative thrombophlebitis (when a vein, generally the internal jugular, becomes inflamed from blood clotting) and septic metastases (basically rotting cells spreading more sepsis throughout the body).
From the patient's point of view, Lemierre's generally starts with a sore throat, fever, and chills, perhaps with a mild headache. Then nausea, vomiting, and difficulty swallowing set in. After that, the patient suffers a cough, pleuritic chest pain, and dehydration (along with brighter urine). There may be some elevated heart rate and minute hemorrhaging. Blood cultures can confirm the presence of Lemierre's syndrome.
Recovery from Lemierre's, assuming it's not fatal (the microorganism which causes it is named Fusobacterium necrophorum, literally "spindle shaped rod which brings death"), takes about six to seven months of hospitalization.
Apologize for how confusing this entry is — this disease is rather complex and difficult to explain clearly.
The important point to realize is: A small infection can travel inward and become very serious very quickly.