The film (Looper) shows us a fast-forwarded timeline, where the character gradually gets older, and the hair loss scenario did not look very realistic there. The character keeps a rather full head of hair all the ways to his 40s. After that the actor is switched from Joseph Gordow-Lewitt to Bruce Willis, and he's now receded to an NW3. In his 50s, the character is shown thinning all the way, and in the later stages, we're left with the NW6/7 guy that we'll see for the rest of the movie.
So what's suspicious about this? Well, we might see a few people hold a full head of head til their 40s and then develop a NW3 with slick bald areas. But the NW3 is at first suspiciously thick, especially for a guy we know is going to be an NW6/7. This starts to thin out in his later years, very abruptly as if there are two isolated stages of MPB going on at separate times (with no overlap between the NW3 and the NW6/7). Any guy balding like this will surely be somewhat of a medical curiosity, to say the least.