Google Site links

I noticed in my webmaster tools that Google is now displaying site links for my Ecommerce store. I’m a bit surprised since my store is only 4 months old. I have been following their best practices and have a lot of really good back links including many deep links. I am curious how many sites are getting site links from Google?

It’s all very difficult to fathom!
Site links are applied automatically, according to some complicated and arcane algorithm. The same site may get one set of site links, a different set of site links, or no site links at all, when you search for essentially the same thing but using slightly different words or word order.

One of my sites sometimes does, and sometimes doesn’t…