Well let's put that to the test. yofie.com vs yfie.com ...which has more value?
I believe brandables are best with a 5-7 letter combination. The key imho isn't having just a handful but instead having a large enough selection for a buyer to choose from. A good end-user buyer might fork over $1k for a solid nonsense brandable like Witza.com.
My opinion in no way means to deter investors from 4Ls but the differences should be noted. I think brandables are a very different target than 4L buyers which for the time being appear to be "collectors" via other domainers.
I am also doubtful that 5Ls will sell out within the next decade but no matter...there are only so many pronouncable combinations.
Oh and btw..I have a neat tool that lets you create random names which could be used to also generate domain names too.
http://www.namefunk.com/random/
hehe...