Depends on your business plans pretty much. If you're appealing to the very internet illiterate, the single letter brand is very useful. However, there might

Depends on your business plans pretty much. If you're appealing to the very internet illiterate, the single letter brand is very useful. However, there might be some problems; eg trademark issues in which case you'll lose the domain to the trademark holder. So, not only do you have a premium for the single letter but you also have to pay lawyer and court costs for it.