Do lots of people get ureaplasma urealyticum infection, or is it unusual?

Fair number. Cause of one of less common stds. Can also cause urethrorrhagia in boys + young men. This is a mild form of posterior urethritis. Lab. Cultures are very pricey and ureaplasma organisms are very difficult to grow. Urethrorragia causes mild stinging upon urination plus mildly bloody urine at the end of voiding. Also drops of blood at the urethral opening + on underpants. Treated with erythromycin.
Unusual infection. Ureaplasma is a common bacteria found in the genitourinary system. Sometimes it causes infections and sometimes it doesn't and we don't know why. Not all tests will diagnose it and sometimes it's unfairly blamed for certain diseases. It should only be treated with antibiotics if it's causing a serious issue that isn't being caused by some other bug.