Interesting. I was not aware that so many TLDs allow single letter domain names. Since so many single letter domain names are for sale, it really seems to be hard to built a brand with a single letter. I personally think that the most important domain names are not the short ones. The most important domain names are the ones with a very big brand. Looking at "google.com" gives me a much stronger signal than looking at "z.com". So the brand really matters.