Size matters. 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: