while "n5.biz" might not be premium, it is brandable and memorable if you aren't concentrating on SEO (Only 1/2 of the equation, and short-sighted if you are trying to build a business, instead of eek out a living ). Short acronyms have always stood the test of time, and it could be that "n5" becomes a popular car, or sports drink, or fertilizer, or anything else. And while the .biz extension isn't huge now, it could be in the future, or it could turn into something perfect for SEO later. Just my .02
these domains are best for brand recognition, and serve as good acronyms. Also, most of the 3 letter and 4 letter domains and below (2 lettered) have all been sold by now. Maybe even the 5 letter ones too.. Too hard to get them now, unless someone is selling them.
another factor is that they are rare.. there is 1296 2 char .com and 46656 3 char .com, which are all registered
Short names, especially 1 and 2 character names, are primarily popular for rarity sake. 2-3 letter names are IMO rightfully popular because of the acronym possibilities with any such name. Once it gets into gibberish 3-character or bad 4-letter names, the rarity factor is barely visible, and the names aren't guaranteed to sell well. Meanwhile, 3-letter .com names are almost impossible to buy for under $2,000 apiece even for bad ones because there are so many willing buyers, mostly domain resellers who like the rarity factor and potential for a company with the initials of the name to give them a handsome profit. Hope that helps. P.S. - I'm new here, but post a lot on other domain forums...hi everyone.
I keep a few around for when I run ads in the newspaper classifieds. Keeps the cost down because they are so short. Some day they might even be worth something