Single Nucleotide Polymorphisms in DNA Testing

Last evening I spoke briefly with a friend of mine who is a genetics professor at a local university. I asked him in passing if I’m missing anything new in genealogical DNA since I first read about Y DNA and mtDNA. He responded with the following in an email:
Single Nucleotide Polymorphisms (SNP’s) are now becoming the most commonly diagnosed markers for molecular genealogy due to sheer numbers and relative ease/low cost of doing the assays.  23andme is the biggest SNP analyzing company and they have a huge database (800,000+) of clients they have surveyed with over 900,000 genome-wide markers (not just on the Y and mtDNA).
Unlike Y DNA tests I’ve seen, which test fewer than 100 “markers” for $100 or less, (he writes that):
A simple saliva test for 900,000+ markers by 23andme now costs just $99.
Also, rather than be limited to a single chromosome (like the Y chromosome) …
… you can trace chromosome segments on the 22 pairs of non-sex chromosomes around in extended families.
As I learn more about SNP, I’ll blog some more.