I stumbled upon this at 9gag.com.
Does your laptop keep running out of power?
No longer! Use the natural power of your own laptop to recharge itself!
Original ‘advertisement’:
USB Laptop Self Charger Cable
REAL LIFE TESTIMONIALS
CCS: this is too frreeaaaking cool la ……… u made me …. cum ….. lol
FC: great lols anyways…how the heck u came up with this lol
AK: WTH…..
KR: wahh… nice thought… You are someone… 
Since there are so many nice testimonials, I thought why not give it a try. I used it on my netbook, HP Mini 210 and tried it out. It turns out like this…
Hands on: USB Laptop Self Charger Cable
However, it seem like not working… I has a sad liao… I want RMA (Return Merhandise Authorization)!!!
P.S. The above post is just for fun. Don’t take it seriously. Such product does not exist.
Reasoning behind this;
F: generally the output from the USB should be low powered, for example your feeding a dinosaur with a chicken
H: it’s a valid argument since your laptop usb only drains it’s battery when you utilizes the usb. So, the principles of conservation of energy cannot be applied.
F: logically, it MIGHT help prolong the battery usage ALITTLE
but its not feasible nor as magical as we might think
AND, dont forget power loss thru journey of resistance of the conductor.
Nice Argument;
K: Can your laptop components produce current to the battery?? LOL
H: You can use your usb to charge your iPhone and power your external HDD. 
