Well, as far as I understand it, blade servers two major several benefits.
Space requirements
Economies of scale
So, unless space is really at a
premium and/or you don't want to install a massive server farm, then why not simply stick with the regular 1U server appliances you already have?
Of course, I'm a wireless guy, not a hosting guy, so I'm only giving my opinion, not professional advice.
Mr Mephisto