Hi EV,
It is my understanding that the dc blocks are required if the splitter is power passive in all ports. here is one example:
http://www.solidsignal.com/pview.asp...s&sku=PV23-602
However, they are not required if one gets say a 2-way that is power passive on one side only. Here is an example:
http://www.solidsignal.com/pview.asp...s&sku=PV23-222
Best,
Rick