The abuses of antibiotics are quite simple. People use them too much, and for illnesses that don't really require them. It is not uncommon for people to take over the counter antibiotics for illnesses that are not caused by bacteria, or to take them in the wrong doses. This makes bacteria resistant to that type of antibiotic, and with serious diseases this can be a big problem. It is not just over the counter medicines either. Prescription antibiotics are often abused, and often because of doctors. Many doctors, whether through incompetence or a money-hungry HMO pressuring them to use cheaper, proven drugs, over-prescribe certain varieties of antibiotic, making them less and less effective.
The damage caused by the misuses of antibiotics goes beyond the damage caused to the drug itself. The people who misuse them often suffer dire consequences, such as the killing of many of the beneficial bacteria that normally reside within your body, doing such important things as aiding in digestion. Extremely strong antibiotics are often prescribed for hospital patients, but these dosages are usually reserved for those people who have serious infections, such as the latter stages of pneumonia. At that point possible desensitization of bacteria and side effects to the patient are the least of the doctor's concerns. It is at this point only that such massive doses of antibiotics should be administered.
Unfortunately, these consequences are not mere hypothetical. Already illnesses are cropping up that are resistant to even the strongest antibiotics. The most disturbing of these is one that was once thought dead: tuberculosis. There are now over 5 identified strains of this deadly illness that are unusually resistant to treatment, and the only known cure is to quarantine the patient. If antibiotics are not used more responsibly in the near future, they may soon become all but useless in fighting certain diseases.