There's a similar product available from MSI.
http://www.msi.com/index.php?func=newsdesc&news_no=1013
Note that the ASUS product claims it works on "any desktop". The MSI product claims it works on their entire product line, includng notebooks, As many of these products pre-date the iPad by many years, it's reasonable to assume that there was no particular hardware design implementation that allows the increased current draw from the USB ports.
The Gigabyte version, referenced earlier, is clearly designed for a specific hardware feature available in their newer products and is likely an entirely different, possibly better, implementation only available for specific products.
I guess we all have to decide for ourselves what risks we're willing to take.