Yes Aspergers can be very mild. It is common for people to have limited traits of a disorder, not just developmental disorders like Aspergers but more common disorders such as Depression, OCD or personality disorders. If you take a look at the diagnostic criteria for Aspergers http://en.wikipedia.org/wiki/Diagnosis_of_Asperger_syndrome you will see that it is defined by specific criteria. There is no reason why a person might not meet some of the criteria and not others. You should also keep in mind that the diagnostic labels we use (such as Aspergers) are an attempt at giving names to constellations of symptoms we see occurring together. They are far, far from perfect.