We all know that Jeremy Piven got a hair transplant! He was noticeably balding around season one of Entourage, but his hair kept getting thicker and his hairline kept getting lower. Now he has a nice full head of hair with a relatively low hairline. As a male Hollywood actor, he just refused to go bald.
That big scar on the back of his head is where the hair follicles were transplanted from his scalp. This "strip scar" is a popular method of performing hair transplant surgery. This solidifies the fact that Jeremy Piven 100% doesn't wear a toupee.
The temporal peaks were filled in and the overall hairline was brought down.
Jeremy Piven's hair transplant definitely came out natural looking. It looks like he's very happy with the result too!