The criteria seems to be that one has a terrible personality, is simultaneously high-maintenance and inconsiderate of others, thinks very highly of one's self, but lacks any other connection with the autism spectrum.
Secondly, people forget that autism, as a spectrum, is being studied further and further and as such, we are finding more reason to believe that it actually does affect a lot of people -- not necessarily that it is grossly misdiagnosed. Furthermore, the number of doctors knowledgeable enough in diagnosing someone at any range of the spectrum is low. As we learn more about it, we are seeing people their 20s, 30s, some even well into their 50s and 60s finally being diagnosed because they were able to adapt well-enough that it seemed nothing was wrong on the outset.
Similarly, females on the spectrum are also often misdiagnosed with anxiety, depression or eating disorders because of how it affects them, and therefore we think that autism primarily affects men even though that may not be the case at all. Society tends to prime girls at a young age to be more sociable (but doesn't frown upon them being shy either), so they are often able hide under the radar, but continue to suffer in other ways. I'm on the spectrum myself, and I've had doctors laugh at me for wanting to be tested because "I 'look' and 'act' 'normal'," to them, which is incredibly insulting. Additionally, those that are trained to detect autism are often pediatricians, not general practitioners that aren't taking into consideration the adult patient's learned-skills over time. This is often what leads people to try to figure out what is wrong with them through other means, and I don't think we should be going around telling other people who they are and aren't. There will always be hypochondriacs, but this is one of those situations where I feel like we should try to take people seriously before we write them off entirely.
So thanks for the armchair neuropsychology, but nobody needs it; we still have a lot to learn.
Speaking of self-diagnosis ...