I recently decided to start doing a little more cable management in my system because it looked really bad. Keep in mind I have a Thermaltake 775 Watt Modular Power Supply
Basically I have a Coolermaster 430 Elite case as my build and I added some Thermaltake fans on the top and side window, well instead of putting having them on their own individual cables that are going to the power supply i took a set of 4pin molex cables out and a set of SATA cables out to free up space and have nicer cable management.
In the act of doing that I sort of mickey mouse rigged the HDD power cable and Internal Cyclone blower to my case fans, very hard to explain but the thermaltake case fans have a sort of double molex on them, one side male the other female and I used a Molex to Sata adapter for the HDD. On on the female Molex side the power is coming into the fan and on the other side is the male Molex power coming in for the HDD to be powered. So it basically looks like this:
http://img707.imageshack.us/f/1199934601.jpg/
I also have this done for the Cyclone blower, all in the name of cable management but in the end I was wondering if it is anymore dangerous than normal cabling for the HDD and Cyclone blower on their own Modular segment.
PS: I also have two of the four case fans directly connected to the motherboard instead of VIA case fan wire ---> 4pin molex adapters.