Size matters.

news.com posted an article about our new blade serversSun defends big blade server: ‘Size matters’.
I tend to view the world like Andy:

"It's not that our blade is too large. It's that the others are too small," he said.

In the case you want expand the usage of blades for bigger workloads you need more processors or cores and you need for I/O. Both requirements leads to more electronics in you blade. With small blades you see two problems:

• Missing space. There is a paradoxon: The more you fill your blade with electronics, the more free space do you need to cool it down (fhere have to be some space for the air flow)
• Slots. The amount of I/O-Slots in a blade is a very precious resource. You can only build a certain amount of slots in a given amout of space. Basic Physics.