I know some people are more likely to get mycoplasma genitalium than others. which ones?

STD: Mycoplasma genitalium apparently causes about 20% of cases of non-gonococcal urethritis. Another 30% are caused by chlamydia species. These cases are often viewed as sexually transmitted diseases. Std's are more frequent in persons who have unprotected sex with increased numbers of sexual partners. I am not aware of other associations. May be more common in men than women.

Unprotected sex: Since mycoplasma genitalium lives on the lining of the uretra in men and the cervix in women, if one has unprotected sex with an infected partner they are more likely to become infected.