Private clouds require considerable upfront investment in both hardware and software, so they are not a good choice for small and medium sized companies operating currently under tight budgets in this economy IMHO. Also, that technology is changing so quickly that if you don't have the skilled IT resources onhand, as well as the financial resources to keep up with it you will find that your "cloud", that you have sunk a lot of money into, will become outdated very quickly as well :-D.