Multiple alleles for blood group? Arnt all genes determined by multiple alleles?

I understand your confusion.  A lot of our more apparent traits seem to be controlled by multiple alleles.  Some of them are controlled or influenced by more than one gene.  While there may be more than one gene, each of these genes only have two alleles.  

For some great examples of traits controlled by genes with just two alleles, you can look at Gregor Mendel's experiment with pea plants.  There are also a bunch of traits that might not have anything to do with outward appearance but are also controlled by genes with just two alleles.  Dyslexia, for example, is a dominant trait controlled by a gene with just two alleles.  The ability to roll your tongue is another one.

*Ear lobes: attached or not attached

*Hair line: straight or widows peak

*Earwax: Wet or Dry

*Dimples

*Freckles