A recent project I was working on where it was critical to change the block sizes when formatting the LUN with VMFS. Apparently the client has some VMs that are thick provisioned in sizes over 300GB per. This is something good to know up-front when considering a new LUN allocation.
The default blocksize is 1MB which only supports up-to 256GB VMDKs. I recommend to customers they move forward with 2MB or even 4MB blocksizes. The 2MB blocksize supports 512GB VMDKs, and the 4MB supports 1TB VMDKs.