until recently asperger's was considered to be on the spectrum and i am sure it will be again
the medical community is always changing its minds about everything and for as much as they know about one subject there is usually twice as much they dont know about the same thing
as far as having a touch of aspergers... sure
that is the same for every illness, disorder, condition, etc... some people get things worse than others
but yeah there are certain things they look for that in the right circumstances can actually keep you from getting a diagnosis. for example my son is in the severe range for autism. he never talked, is hugely delayed in most mental/social areas... but because he liked to cuddle and showed affection towards his parents then our doctor was hesitant to have him evaluated.
here is the "official" word on what causes autism spectrum disorder (aspergers included) "it is caused by a combination of genetic and enviromental factors" so basically they have no clue.
there are some distinct genes that doctors have decided have tributed to autism but they are common in most people they just dont always get "switched on", or so i have been told. so if that follows then yes there is a genetic factor but the theory is that it usually takes an enviromental factor to switch those genes on. basically i just say its all hog wash and love my kid no matter how he is... and we have also gone ahead and had another child so i am not too worried about the genetic bit too much